I decided to hop into the test map to find out how low you need to go to survive a fall from a plane and here are the results.
1,000+m=Instant Death
500m=Instant Death
250m=Instant Death
100m=Instant Death
50m=Instant Death
25m=Instant Death
15m=Can survive with a medkit
1-10m=Can survive without a medkit.
Margin of error of 2-3m.
Ground in test was at 22m on ALT gauge so make sure you know where you plan to land because on Normandy Campaign 0m is sea level where on a Moscow map it would be the lowest point there.