THIS HAPPENS WITH A 360 CONTROLLER. The map and vertical climb button are the same!

Start on foot.
Approach helecopter.
Get in as driver.
While animation for getting in is played, press the map/climb button.
Dick around with the map, close it.
Your neck may be broken and the camera may rotate on a strange and confusing axis.

The timing on this may make it difficult to reproduce. You can fix it by hopping out and back into the helicopter.