H. Finn: In the US, the requirement to maintain the last assigned altitude, when cleared for an instrument approach, happened because of a B-727 which crashed into mountains in Virginia near Wash. Dulles Airport (IAD). This was in the 70s.
This crash also inspired the creation and requirement of the GPWS. The B-727 carried regular passengers. If it had been a freight airplane, less would have resulted regarding safety certification.