Meanwhile, you had a series of Boeing 707 and 747 accidents spanning 25 years, which were due to an engine pylon design flaw that was ported over from the 707 to the 747, and which caused several fatal accidents before it was finally resolved.

- In 1968 BOAC 712 (a 707) had an uncontained engine failure followed by an engine departing, resulting in an intense blaze that could not be extinguished (since the fire suppression system was within the engine nacelle that had fallen off). A successful emergency landing was made but not everybody got off the plane before it was consumed by fire.

- In 1987, a TransBrazil 707 lost one engine in flight due to the design issue. It made a successful emergency landing.

- In 1991, China Air Cargo 358 (a 747) had two engines fall off (no 3 detaching and taking no 4 with it) resulting in the death of all five crew.

- In 1992, Trans-Air Service 671 (a 707) had two engines fall off (no 3 detaching and taking no 4 with it). The aircraft made a successful emergency landing.

- Also in 1992, a month after Trans-Air 671, another 707, this time flown by Tampa Colombiana, had an engine fall off. It made a successful emergency landing.

- Still in 1992, six months after the Tampa Colombiana accident, an El Al Cargo 747 lost engines 3 and 4 after take-off from Amsterdam. The aircraft not only lost the engines but also hydraulics for the flaps on the affected wing; when it deployed its flaps only those on the left side deployed, creating an asymmetric lift condition which made the aircraft uncontrollable. The aircraft flipped and crashed right into residential housing, killing both the crew and dozens on the ground.

- Early in 1993, Japan Air Lines Cargo 46E, a 747, lost its number 2 engine when the pylon failed on that one. The aircraft made a successful emergency landing.

Seperately, there's TWA flight 800, the 747 that went down near New York in 1996. This was a dual design issue - the center-wing fuel tank was heated up by an air conditioning unit which had been designed in proximity to the tank - causing a large amount of fuel vapors; these vapors had then been ignited by a short-circuited fuel quantity meter. The presence of both heat sources near to, and potential ignition points within the center-wing tank were noted as two design flaws in the accident report.

The 737 had two notorious series of accidents following design issues:

- The Dual Servo Valve failures on the rudder power control unit that brought down two 737s and very nearly brought down a third in the early 1990s (United 585 - fatal; USAir 427 - fatal; and Eastwind 517 - crew lost control twice but managed to bring the aircraft home); this was traced to a design fault on the power control unit which Boeing was forced to rectify.

- And the TCAS failures on the Boeing 737MAX in the late 2010s which brought down two 737s (LionAir 610 and Ethiopian 302 - both fatal) and which stemmed from a poor design and implementation of the TCAS feature, including its reliance on just a single data probe - something Boeing already KNEW could cause issues (see the Birgenair 301 and Aeroperú 603 accidents, both involving Boeing 757s in 1996 - and both due to data probe blockages); and the fact that TCAS would reset to default after every control imput, meaning that if it malfunctioned it would keep imputting the wrong commands over and over again.