Piper Aircraft · Twin-engine piston plane
Piper PA-23 Apache/Aztec and PA-30/39 Twin Comanche
Is the Piper PA-23 Apache/Aztec and PA-30/39 Twin Comanche safe? It ranks Shared rankWithin 1 point of other aircraft types: the difference is not meaningful.More in the glossary of 23 small planes we rate, with 40 fatal accidents counted in about 3.4 million US flights since 2008.
Likely range 36 to 47
How the score is built
- Fatal accidents
- 40 in 3.4 million flights
11.7 fatal accidents per million flights. Counted: all civil flights in the United States since 2008 (private, training, charter and other), accidents and unexplained losses; not counted: accidents outside the United States or before 2008, military, test and illegal flights, sabotage, hijackings, shoot-downs and deliberate crew acts.
- Full-loss equivalents
- 39.1
Each counted accident adds the share of people on board who died (1 = no survivors). This is what the score is based on.
- Flights flown
- 3.4 million
Estimated flights of all kinds in the United States since 2008. Flights of all kinds in the United States (private, training, charter and other civil use) 2008 to 3 November 2026, each counted from take-off to final landing: the hours of all US piston twins in each year (active aircraft and hours from the FAA General Aviation and Part 135 Activity Survey), split between types by US-registered aircraft (FAA register, 2,123 of this type in 2024) times how much each type flies against its class (0.80, mostly from airframe hours in NTSB accident records, partly from hours per aircraft seen by ADS-B receivers in 2019-2022), at 1.12 hours per flight from ADS-B tracks: about 72 flights per registered aircraft per year in 2024. Flights and accidents outside the United States, or before 2008, are not used. Against the FAA's hours per helicopter model, this method is off by about 22% on a typical type. Uncertainty roughly ±25%.
- Technology generation
- Twin-engine piston plane
Small fleets are pulled toward the record of the other types of their generation: 10.9 full-loss equivalents per million flights over 17.6 million flights. Weight of this family's own record: 92%.
- Likely range
- 36 to 47
The score is 90% likely to lie in this range, given how few accidents a type has and the error in the estimate of its flights.
- Last fatal accident
- 17 December 2025
Private, West Chicago, IL, United States of America: 2 of 2 people on board died.
- Aircraft destroyed
- 22
Aircraft the NTSB coded as destroyed in an accident in the United States since 2008, fatal or not, from all causes. The NTSB codes many wrecks as only substantially damaged, so the real number is higher (context only, not in the score).
Compared with everyday risks
One flight on the Piper PA-23 Apache/Aztec and PA-30/39 Twin Comanche carries about the same risk of death as the activities near it below.
- An hour's walk1 in 14 million
- Driving 100 miles (160 km)1 in 5.9 million
- An ordinary day: accidents and violence1 in 1 million
- A day of skiing1 in 830,000
- A scuba dive1 in 500,000
- Cycling 100 miles (160 km)1 in 430,000
- Running a marathon1 in 290,000
- A skydive1 in 250,000
- A general anaesthetic1 in 100,000
- One flight on the Piper PA-23 Apache/Aztec and PA-30/39 Twin ComancheThis aircraft1 in 88,000
- Riding a motorbike 100 miles (160 km)1 in 83,000
Accident history
40 fatal accidents in the United States since 2008 count toward the score, with 76 people on board killed.
| Date | Flight | Killed | What happened |
|---|---|---|---|
| PrivatePiper PA-30 · West Chicago, IL, United States of America | 2 killed / 2 on board | Just after takeoff from DuPage Airport near Chicago, the PA-30 drifted right, rose to about 75 ft nose-high, banked left and right, then rolled to about 90 degrees right and hit the ground; both pilots died. The engines sounded normal. The investigation has not published a cause.Cause not yet established; counted.Type: Loss of control in flightNTSB docket | |
| Blue Wave Air LLCPiper PA-23-250 · Condon, MT, United States of America | 3 killed / 3 on board | Flying from Billings to Polson, Montana, the PA-23-250 met icing and had a left-engine problem; unable to hold altitude, the pilot declared an emergency and it crashed in the Bob Marshall Wilderness near Condon. Three died. The investigation has not published a cause.Cause not yet established; counted.Type: IcingNTSB docket | |
| PrivatePiper PA-30 · Sherman, TX, United States of America | 1 killed / 1 on board | Cruising towards Sherman, Texas, the PA-30 had right engine fuel surges, then the left engine stopped; the pilot had likely turned its fuel selector off by mistake. Gliding into a field at low speed, it rolled and hit nose-down. He died. NTSB: loss of control in a forced landing.Type: FuelNTSB docket | |
| Midcoast Aviation ServicesPiper PA-30 · Claxton, GA, United States of America | 3 killed / 3 on board | After a fuel pump failure left them with under a gallon of new fuel, three pilots on a lesson took off from Claxton, Georgia; the PA-30's right engine starved and it hit trees within half a mile. All three died. NTSB: poor fuel management caused the power loss.Type: FuelNTSB docket | |
| PrivatePiper PA-30 · Ebensburg, PA, United States of America | 2 killed / 2 on board | Taking off in darkness from Ebensburg, Pennsylvania, into low cloud, the PA-30 climbed in a left turn through about 360 degrees, then hit trees in a steep bank 2 miles south; both on board died. No fault was found. NTSB: spatial disorientation and loss of control.Type: Loss of control in flightNTSB docket | |
| PrivatePiper PA-30 · Winston-salem, NC, United States of America | 2 killed / 2 on board | Approaching Winston-Salem, the pilot of the PA-30 said one engine was weak, flew past two runways, then rolled inverted at treetop height and dived; both on board died. NTSB: a faulty fuel servo cut right engine power; he did not land at once, feather it or keep Vmc.Type: Engine failureNTSB docket | |
| PrivatePiper PA-30 · Pond Creek, OK, United States of America | 3 killed / 3 on board | A pilot with no instrument rating flew the PA-30 at 16,500 ft for about 90 minutes with no oxygen masks on board, then descended into cloud near Pond Creek, Oklahoma, spun and broke up; all three died. NTSB: loss of control; hypoxia and disorientation were possible.Type: Loss of control in flightNTSB docket | |
| PrivatePiper PA30 · Rock Hill, SC, United States of America | 1 killed / 1 on board | Nearing Rock Hill, South Carolina, in his newly bought PA-30, the pilot circled for 45 minutes on the phone with a mechanic about a gear warning, let the speed drop and stalled at low height; he died. The gear was in fact down. NTSB: a stall while he dealt with a gear indication.Type: Loss of control in flightNTSB docket | |
| PrivatePiper PA23 · Gulf of Mexico | 1 killed / 1 on board | At night, without talking to air traffic control, the PA-23-250 flying from Cape Girardeau, Missouri, toward Gonzales, Louisiana, descended into the Gulf of Mexico; the pilot is presumed dead and the NTSB could not determine why.Cause not yet established; counted.Type: Unknown causeNTSB docket | |
| PrivatePiper PA30 · Naples, FL, United States of America | 1 killed / 1 on board | On approach to Naples, Florida, the PA-30 left its path without a radio call, descended and hit the ground; the pilot died. Remains of a 3.8 lb black vulture were in the wreckage. NTSB: the bird broke through the windshield and incapacitated the pilot.Type: Bird strikeNTSB docket | |
| Unknown operatorPiper PA23 · Pahokee, FL, United States of America | 5 killed / 5 on board | Descending toward North Palm Beach County airport from Tampa, the PA-23-250 lost power on one engine for reasons the NTSB could not find; maneuvering to land on one engine, the pilot lost control near Pahokee, Florida. He and four passengers died.Cause not yet established; counted.Type: Engine failureNTSB docket | |
| PrivatePiper PA23 · Ellensburg, WA, United States of America | 1 killed / 1 on board | Minutes after leaving Ellensburg, Washington, for Yakima, the instrument-rated pilot of the PA-23-250 became spatially disoriented, lost control and crashed; he died.Type: Loss of control in flightNTSB docket | |
| PrivatePiper PA23 · Beaver Island, MI, United States of America | 1 killed / 1 on board | Taking off on a dark night from Beaver Island, Michigan, with no horizon or ground lights, the Apache turned north and flew into woods a third of a mile from the airport; the pilot died. No fault was found. NTSB: the pilot did not keep a positive climb after takeoff.Type: Flight into terrainNTSB docket | |
| Air America Flight CenterPiper PA23-250 · Elko, NV, United States of America | 1 killed / 1 on board | On a night positioning flight from Sacramento to Salt Lake City, the PA-23-250 crossed mountains into forecast cloud, icing and mountain wave and descended out of control into terrain 42 miles south of Elko, Nevada. The commercial pilot died.Type: Loss of control in flightNTSB docket | |
| IndividualPiper PA30 · Topeka, KS, United States of America | 2 killed / 2 on board | On a practice checkride for a multi-engine rating at Topeka, Kansas, after simulated engine failures, the PA-30 hit the ground in a slow, left-wing-low attitude near the runway 18 threshold; the instructor and student died. NTSB: both pilots did not keep control in the circuit.Type: Loss of control in flightNTSB docket | |
| PrivatePiper PA23 · Chatsworth, GA, United States of America | 4 killed / 4 on board | Flying his family home from Tuskegee, Alabama, the pilot, who had no instrument rating, kept going into storms near Chatsworth, Georgia; the PA-23 went out of control in severe convection and broke up in flight. He and three passengers died.Type: Windshear or stormNTSB docket | |
| PrivatePiper PA30 · Haines, AK, United States of America | 2 killed / 3 on board | Flying to Haines, Alaska, the pilot of the PA-30 shut down the right engine to show a restart, but a weak battery and dead alternators stopped it restarting. After a low pass over a strip he turned towards the dead engine, stalled and hit the shore; two of three died.Type: Loss of control in flightNTSB docket | |
| PrivatePiper PA30 · Plainfield, IL, United States of America | 1 killed / 1 on board | Climbing to avoid storms near Chicago's Class B airspace, the PA-30 slowed to about 48 kt and stalled, then dived in turns to 211 kt and broke up over South Plainfield, Illinois. The pilot died. NTSB: loss of control in a climb near storms, then a stall and breakup.Type: Loss of control in flightNTSB docket | |
| PrivatePiper PA23-150 · Hayward, CA, United States of America | 1 killed / 1 on board | Returning to Hayward, California, the pilot of the Apache reported left engine trouble and turned towards a field; it rolled into a steep left bank and hit a building. He died. NTSB: water in the fuel stopped the left engine and he let the speed fall below Vmc.Type: FuelNTSB docket | |
| Sowards Aircraft Leasing, LLCPiper PA30 · St. Petersburg, FL, United States of America | 1 killed / 1 on board | Doing touch-and-goes at St. Petersburg-Clearwater to learn the PA-30, a pilot new to the type lost right engine power, feathered it and let the speed drop; it rolled right and hit the ground beside the runway. He died. NTSB: below Vmc after a power loss of unknown cause.Cause not yet established; counted.Type: Loss of control in flightNTSB docket | |
| Tailwheels Etc., Inc.Piper PA-23 · Lakeland, FL, United States of America | 2 killed / 2 on board | On a multi-engine lesson near Lakeland, Florida, likely during a simulated right engine failure, the Apache slowed, turned right, pitched down and dived into a building; the instructor and student died. The rudder cable was slack. NTSB: loss of control, cause unknown.Cause not yet established; counted.Type: Loss of control in flightNTSB docket | |
| Eagle Support Services LLCPiper PA23-160 · Port Clinton, OH, United States of America | 1 killed / 1 on board | Leaving Port Clinton, Ohio, the Apache made popping noises, struggled to climb with an apparent left engine problem, turned left and dived into the ground; the pilot died. NTSB: loss of control after a left engine power loss for reasons that could not be determined.Cause not yet established; counted.Type: Engine failureNTSB docket | |
| PrivatePiper PA-30 · Biglerville, PA, United States of America | 2 killed / 2 on board | Flying at night from Bloomsburg, Pennsylvania, a pilot with no instrument rating and little night time likely flew into snow and cloud; the PA-30 turned several times, entered a descending turn and hit the ground near Biglerville. Both died. NTSB: spatial disorientation.Type: Loss of control in flightNTSB docket | |
| PrivatePiper PA-23-160 · Graniteville, SC, United States of America | 1 killed / 1 on board | Just after a night takeoff from Twin Lakes, South Carolina, the Apache's left engine quit; the pilot turned back without feathering it or raising the gear, lost control and hit trees. He died. NTSB: his own faulty fuel valve work starved the engine; speed fell below Vmc.Type: FuelNTSB docket | |
| Garlam Aviation COPiper PA23-250 · Caledonia, MN, United States of America | 3 killed / 4 on board | Arriving at Houston County Airport, Caledonia, Minnesota, from Troy, Michigan, the PA-23-250 Aztec went out of control and hit the ground; the pilot and two passengers died and one passenger was seriously hurt. The NTSB found no fault with the aircraft.Cause not yet established; counted.Type: Loss of control in flightNTSB docket | |
| PrivatePiper PA-30 · Amarillo, TX, United States of America | 1 killed / 1 on board | Minutes after leaving Tradewind Airport, Amarillo, the pilot of the PA-30 reported his left engine had stopped and flew back slowly; it turned sharply left and dived into a yard. He died. The left fuel strainer was 75% water. NTSB: loss of control after the power loss.Type: FuelNTSB docket | |
| PrivatePiper PA-30 · Idaho Falls, ID, United States of America | 2 killed / 3 on board | Shortly after takeoff from Idaho Falls on a hot day, the overweight PA-30's right engine surged; it banked sharply right, stalled and hit the ground near the airport. Two of three on board died. NTSB: water in the fuel cut power, then loss of control; poor preflight check.Type: FuelNTSB docket | |
| PrivatePiper PA-30 · Jasper, AL, United States of America | 3 killed / 3 on board | A student pilot with about 10 hours, no multi-engine, night or instrument training and no permission from the owner took the PA-30 with two others into night cloud at Jasper, Alabama; it crashed in woods a mile away and all three died. NTSB: poor judgment, loss of control.Type: Loss of control in flightNTSB docket | |
| PrivatePiper PA-23-250 · Bullard, TX, United States of America | 1 killed / 1 on board | On a flight from Houston to Tyler, Texas, the commercial pilot flew a maneuver that overstressed the PA-23-250 Aztec; it broke up in flight near Bullard and he died.Type: Loss of control in flightNTSB docket | |
| PrivatePiper PA-23-150 · Canton, MO, United States of America | 2 killed / 2 on board | Heavy on a hot day, the Apache lost its left engine and could not hold height; it hit a tree in a field near Canton, Missouri, and both on board died. The pilot, its own mechanic, had sealed the fuel strainer wrongly. NTSB: a poor choice of field after the power loss.Type: Engine failureNTSB docket | |
| PrivatePiper PA-23 · Millersburg, OH, United States of America | 3 killed / 3 on board | Unable to find his fog-covered destination at night, the pilot of the Apache changed plans several times, then circled the airport at Millersburg, Ohio, and hit trees on rising ground beside it; all three died. NTSB: no terrain clearance in fog, after poor planning.Type: Flight into terrainNTSB docket | |
| PrivatePiper PA-23 · Rochester, MN, United States of America | 3 killed / 3 on board | On a night flight, the pilot of the Apache radioed that his left engine had quit and he might not reach Rochester, Minnesota; it hit trees about a mile from the runway. All three on board died. NTSB: power loss and loss of control for undetermined reasons.Cause not yet established; counted.Type: Engine failureNTSB docket | |
| PrivatePiper PA-30 · Merced, CA, United States of America | 1 killed / 1 on board | An 88-year-old pilot flying the PA-30 to check properties at Merced, California, radioed trouble in the cockpit and hit a pole and a highway bank 3 miles out; he died. He had cancer and diabetes he had not reported. NTSB: incapacitation from several illnesses.Type: OtherNTSB docket | |
| PrivatePiper PA-30 · Amarillo, TX, United States of America | 2 killed / 2 on board | About a minute after a business flight took off from Tradewind Airport, Amarillo, the PA-30 turned back low and hit a warehouse; both on board died. Both engines had water in their fuel and the fuel caps were worn. NTSB: the pilot did not find the water before flight.Type: FuelNTSB docket | |
| Harvey W. Kiniken, JRPiper PA-30 · Port Mansfield, TX, United States of America | 2 killed / 2 on board | Making a night visual approach in haze to Port Mansfield, Texas, the PA-30 flew past the airport, turned towards the shore and hit the shallow Laguna Madre 1.6 miles away; both on board died. NTSB: the pilot did not keep clear of the water on approach.Type: Flight into terrainNTSB docket | |
| PrivatePiper PA-30 · Raneille, WV, United States of America | 1 killed / 1 on board | Flying home at night against advice to stop, the pilot of the newly bought PA-30 flew a weaving low course in poor weather and hit trees on rising ground near Rainelle, West Virginia. He died. NTSB: visual flight into worsening night weather and flight into terrain.Type: Flight into terrainNTSB docket | |
| PrivatePiper PA-23-250 · Summerville, SC, United States of America | 4 killed / 4 on board | Taking off at night from Summerville, South Carolina, for Fort Pierce, Florida, the PA-23-250 Aztec hit trees just past the runway; the commercial pilot and owner and three passengers died. The NTSB could not determine why.Cause not yet established; counted.Type: Flight into terrainNTSB docket | |
| PrivatePiper PA-30 · Selmer, TN, United States of America | 1 killed / 1 on board | Flying VFR at night in rain under a 500 ft ceiling, a pilot with no instrument rating and an expired medical flew the PA-30 into a cornfield near Selmer, Tennessee; he died. He had had two strokes and heart surgery. NTSB: failure to avoid terrain at night in cloud.Type: Flight into terrainNTSB docket | |
| PrivatePiper PA-23 · Highlands, NC, United States of America | 2 killed / 2 on board | On his first flight in the Apache he had just bought, an airline pilot flew into extreme thunderstorms near Highlands, North Carolina, and the aircraft broke up; both on board died. NTSB: he chose to fly into storms; the controller had not described them fully.Type: Windshear or stormNTSB docket | |
| Unknown operatorPiper PA-23-250 · Sterling, KS, United States of America | 1 killed / 1 on board | On a positioning flight from Wichita to Hays, Kansas, for a canceled-check courier run, the PA-23-250 Aztec lost pitch control in cruise when the stabilator trim actuator came apart after poor maintenance; it crashed near Sterling and the pilot died.Type: System failureNTSB docket |
Listed but not counted
These events happened on military, test or illegal flights, or were caused by a crime or a deliberate act, which says little about the aircraft design.
| Date | Flight | Killed | Why not counted |
|---|---|---|---|
| PrivatePiper PA30 · Marion, IN, United States of America | 1 killed / 1 on board | Test flight. On a test flight after his own work on the fuel system, a pilot-mechanic's PA-30 lost left engine power after takeoff from Marion, Indiana, entered a spiral dive in a left turn and hit the ground; he died. NTSB: a stall after the power loss, likely from a fuel system fault.Type: Loss of control in flightNTSB docket |
The NTSB lists 3 more fatal events of the Piper PA-23 Apache/Aztec and PA-30/39 Twin Comanche in Puerto Rico, the US Virgin Islands or another US territory, or on a route outside the US states. They are not used, because the flight count covers US flights since 2008 only.
Old does not mean worst here. The Piper PA-23 Apache and Aztec and the PA-30 Twin Comanche, built from the 1950s to the early 1980s, sit in the middle of the small twins we rate: behind the Piper Seminole, Seneca and Navajo, and a little ahead of the Beechcraft Baron and the Cessna 310 and 340, though the likely ranges overlap. Up to 28 October 2026 we count 40 fatal accidents on US flights since 2008 and 76 deaths, over about 3.4 million flights. On our estimates, the rate per flight is several times that of a Cessna 172. Confidence is medium, and the limits below matter.
What are they?
The PA-23 Apache first flew in 1952, and the PA-23-250 Aztec followed it. The PA-30 Twin Comanche, and later PA-39 with counter-rotating propellers, is a smaller, faster low-wing twin with about five seats. About 9,100 were built. The FAA register shows about 2,120 in 2024, down from about 2,960 in 2014. Nearly all are owner-flown.
What does the record show?
| Flight purpose | Counted accidents |
|---|---|
| Private and other | 35 |
| Training | 3 |
| Ferry and positioning | 2 |
One excluded test flight (2018) brings the total listed to 41. Loss of control in flight leads with 15, then fuel problems (7), flights into terrain (6) and powerplant failures (5). The rest are a flight-control failure, two weather break-ups, icing, a bird strike, one case of pilot health and a night descent into the Gulf of Mexico in 2019 whose cause the NTSB could not determine.
Why fuel and engines keep appearing
Fuel and engine problems together make up 12 of the 40. On 17 February 2010 both engines of a Twin Comanche had water in the fuel when it hit a warehouse about a minute after leaving Amarillo, Texas. On 19 June 2016 an Apache returned to Hayward, California, with left engine trouble and rolled into a building; the NTSB found water in the fuel. On 25 June 2023 three pilots on a lesson took on less than a gallon at Claxton, Georgia, when the fuelling equipment failed; they took off anyway, the right engine starved and all three died.
Old tanks, sumps and fuel selectors need regular checks. Twin pilots also need to treat an engine failure as an emergency with a set drill. On 27 May 2017, a pilot near Haines, Alaska, shut down an engine to demonstrate a restart and the battery could not do it; two of three died. On 22 January 2015 an Apache on a multi-engine lesson at Lakeland, Florida, dived into a building, probably during a simulated engine failure; the instructor and student died.
Does their age matter?
Several accidents involved a recently bought plane or a pilot new to the type. Two Aztecs crashed after control parts failed through poor maintenance: a stabilator trim actuator near Sterling, Kansas, in 2008 and a fatigued aileron cable near Hemet, California, in 2020. The Hemet aircraft does not count, because the FAA register lists it as experimental, and we leave those records out of both the flights and the accidents. The data does not point to a flaw in any of the three designs.
Limits of this result
The flights behind it come from the FAA aircraft register and the FAA General Aviation survey, which gives flying hours for light twins as a class. Airframe hours in NTSB accident records and, to a lesser degree, ADS-B tracks from 2019 to 2022 show these old owner-flown twins flying well below the average twin, and our count takes that into account. Aircraft without ADS-B are not seen and the NTSB hours come only from aircraft that crashed, so the estimate is still uncertain. A flight in any small plane carries far more risk than an airline flight.
The NTSB has not published a cause for the PA-30 crash at DuPage Airport, Illinois, on 17 December 2025, or for the Aztec crash near Condon, Montana, on 17 October 2025.
Before you fly in one
- Ask for the pilot's multi-engine time and recent engine-out practice.
- Ask when the fuel system and the sumps were last inspected, and how much fuel the flight starts with.
- For training, pick a school and instructor with many hours on the type.
- Look up the aircraft's registration in the NTSB and FAA databases.
Spotting one on a tracker
Trackers show PA23 or PA30. Compare the Piper Seneca and the small planes ranking. The method explains the score.
Questions people ask
Is the Piper Twin Comanche a safe plane?
In our data it sits in the middle of the light twins. Up to 28 October 2026 we count 40 fatal accidents on US flights since 2008 for the Apache, Aztec and Twin Comanche together, over about 3.4 million flights. On our estimates, that is several times the rate per flight of a Cessna 172, behind the Piper Seminole and Seneca, and a little better than the Cessna twins, though their likely ranges overlap.
What is the difference between a Piper Apache and an Aztec?
The Apache is the original PA-23 of the 1950s. The Aztec is its larger and more powerful PA-23-250 development. The Twin Comanche PA-30 is a smaller, newer and faster design. We rate them as one family.
Are Piper Apaches and Twin Comanches good for flight training?
They have been used for multi-engine training, and three counted accidents were training flights. Choose a school with an instructor who has many hours on the type, and ask about its engine-failure drills.
Can a Twin Comanche fly on one engine?
Yes, in the right conditions, but it has limited climb on one engine and loses more as the day gets hot or the plane gets heavy. Two accidents in our data, a PA-30 taking off from Idaho Falls and an Apache in cruise near Canton, Missouri, involved a heavy aircraft on a hot day losing an engine.
Sources
- 1.NTSB docket: Piper PA-30, West Chicago, Illinois, 17 December 2025 (opens in a new tab) · National Transportation Safety Board
- 2.NTSB docket: Piper PA-30, Claxton, Georgia, 25 June 2023 (opens in a new tab) · National Transportation Safety Board
- 3.NTSB docket: Piper PA30, Haines, Alaska, 27 May 2017 (opens in a new tab) · National Transportation Safety Board
- 4.NTSB docket: Piper PA-23, Lakeland, Florida, 22 January 2015 (opens in a new tab) · National Transportation Safety Board
- 5.NTSB docket: Piper PA23-150, Hayward, California, 19 June 2016 (opens in a new tab) · National Transportation Safety Board
- 6.NTSB docket: Piper PA-30, Amarillo, Texas, 17 February 2010 (opens in a new tab) · National Transportation Safety Board
- 7.NTSB docket: Piper PA-23-250 Aztec, near Sterling, Kansas, 13 February 2008 (opens in a new tab) · National Transportation Safety Board
- 8.NTSB docket: Piper PA-23-250 Aztec, near Hemet, California, 30 April 2020 (opens in a new tab) · National Transportation Safety Board
- 9.NTSB docket: Piper PA-23-250 Aztec, near Condon, Montana, 17 October 2025 (opens in a new tab) · National Transportation Safety Board
- 10.SafetyScorer exposure model: FAA aircraft register, FAA General Aviation and Part 135 Activity Survey, OpenSky ADS-B, NTSB airframe hours (opens in a new tab)Flights of all kinds in the United States (private, training, charter and other civil use) 2008 to 3 November 2026, each counted from take-off to final landing: the hours of all US piston twins in each year (active aircraft and hours from the FAA General Aviation and Part 135 Activity Survey), split between types by US-registered aircraft (FAA register, 2,123 of this type in 2024) times how much each type flies against its class (0.80, mostly from airframe hours in NTSB accident records, partly from hours per aircraft seen by ADS-B receivers in 2019-2022), at 1.12 hours per flight from ADS-B tracks: about 72 flights per registered aircraft per year in 2024. Flights and accidents outside the United States, or before 2008, are not used. Against the FAA's hours per helicopter model, this method is off by about 22% on a typical type. Uncertainty roughly ±25%.