Air New Zealand Flight 901 (1979)

DC-10 crash into Mount Erebus in Antarctica resulted in changes to flight navigation and training. This was the worst crash in aviation history. It crashed on the lower slopes of Mt. Erebus. All 237 passengers died, and not one survived. The plane originally departed on a sightseeing tour of Antarctica. Investigators assumed the main cause of the crash was due to changes in the flight plan, and the management computer which was not on properly (NZ History).

Delta Air Lines Flight 191 (1985)

When this Lockheed L-1011 crashed, it led to major changes in weather-related flight procedures to prevent something as detrimental as this crash in 1985. A microburst in a thunderstorm caused the plane to come crashing down from the sky, while it attempted to land. After this crash, it forced the FAA to require all commercial flights to detect low-level wind shear (Fox Weather).