Hi, I want to believe that most of you know this already, but after watching a few speedruns of GTA IV I've found that not a lot of people are moving their vehicle mid-air if they are about to land dangerously or similar. I've found that I can save myself from bad crashes and flips by just spinning my vehicle or rolling right or left.

Rolling: Hold "A" to roll to the Left. Hold "D" to roll to the Right.

Flipping: Left Shift will make a Frontflip. Left CTRL will make a Backflip.

Spinning: Hold HANDBRAKE and A to spin Left. Hold HANDBRAKE and D to spin Right.

Cars and Trucks can do Roll, Flip and Spin Bikes can do Flip and Spin Boats can do Flip

Something to note is that the heavier a vehicle is the slower it will Roll, Flip, Spin around.