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Most of the breakups involved clear air turbulence as well, the type that still can't be detected today.
Examples like:
Boeing 707 (BOAC Flight 911) - which crashed near Mt Fuji
BAC One-Eleven breakup in the 60's
Fairchild F-27B broke up in turbulence over Alaska
Fokker F-28 broke up in turbulence after flying into a ''microburst'' in 1981
De Havilland Comet broke up after flying into a storm in the 1950's.
Modern Day airliners (or even those built in the 1970s like DC-10) are built to withstand really high G-Forces. Despite the certification requirements for civil aircraft are +2.5G and -1G.
Federal Express (FedEx) Flight 705: Highlighted parts of the Incident include, the aircraft (a DC-10) being steeply pitched up 15°, then using ailerons to roll the aircraft to 140° attitude (way past the certification of maximum 60°).
The aircraft was flying upside-down, with its engines at full-power, this caused the mach tuck effect (the airflow over the wings reached the speed of sound).
During Landing, the aircraft was 16,000kg overweight, really high, really fast. Captain Sanders made really sharp turns (again exceeding the DC-10's certified limits) and landed the DC-10 just as it feels in a normal landing. Despite it being damaged, it was flyable and is in service with FedEx as of May 2022
| 1986 | 2015 |
|---|---|
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China Airlines Flight 006: On 19 February 1985, High altitude upset and 30,000 ft dive due to spatial disorientation after failure of Engine 4. The failure of Engine 4 lead to asymmetrical thrust and the aircraft began to yaw. This was compensated by the Autopilot using the ailerons. Due to the autopilot using ailerons instead of rudders (The rudder could not be deflected by the Autopilot on that aircraft) to compensate for asymmetrical thrust, the aircraft kept yawing despite completely turning the yoke (100% aileron deflected)
The crew realized the aircraft was banking, the crew was disoriented, they thought the autopilot was not performing corrective actions (rather, not working) and hence disengaged it. As soon as A/P was disengaged, the ailerons no longer compensated the yaw and the PF neither gave rudder or aileron inputs causing the aircraft to bank instantly leading to an uncontrollable descent.
When on ground, it was noted that the landing gear doors broke apart, a lot of the vertical stabilizer was missing from the aircraft, and the G-Forces of about 5G (for 2½ minutes) caused the wings to permanently bend (but not break) but still it landed safely. Despite such damage, repairs were done and the aircraft was used till late 2014.
| Attitude | Damage Caused |
|---|---|
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Such incidents prove that, airliners built today are capable of withstanding high G-Forces without disintegrating mid-air. But windshear (microbursts) is still a concern.
The above incidents prove that aircraft built today (the DC10, MD11, A320/50/80) are highly durable and so explains most of the incidents of mid-air breakup you mentioned. But, they are prone to another problem. Windshear during approach. There have been multiple incidents in the 80s (even in the 90s) where windshear has caused aircraft (even a 737) to smash into the runway (or ground) while landing (United Airlines Flight 585)
| Downdraft | Windshear |
|---|---|
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Source: https://safetyfirst.airbus.com/wind-shear-an-invisible-enemy-to-pilots/
But, Modern day airliners have Windshear Detection systems onboard and inform the crew about a potential windshear well before getting into it. The airports are equipped with LLWAS (Low Level Windshear Alert System) whose alerts can be communicated by ATC to the crew.
This concludes that, due to LLWAS and onboard windshear detectors and also highly durable aircraft makes disintegration due to turbulence a really, really rare scenario.
| Potential Windshear Alert | Currently in Windshear |
|---|---|
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Fun Fact: The De Havilland Comet which you mentioned was so much less durable that, its first version (Comet 1) used to disintegrate due to explosive decompression caused by metal fatigue after a year from manufacture. It had square windows which caused high stresses in the corners due to repeated compression/decompression cycles on each takeoff/landing causing the fuselage to fail. BOAC (British Airways) Flight 781 and South African Airways Flight 201 both crashed in 1954 due to the design and was grounded as it became evident that all Comets were going to explode mid-air. However, De Havilland rectified this issue and launched the Comet 1A (not sure of the model number) but meanwhile the Boeing 707 was launched and airlines preferred Boeing 707 over the Comet. The Comet's last model was Comet 4C which retired in 1997.
