Flying vehicle not flying anymore in 1.5

Hi

I made a flying vehicle in 1.4 that worked fine
since updating to 1.5 it doesn't fly anymore although it still acts like a flying vehicle (floating above the ground, mountable etc)

I think it may have something to do with key mapping but the buggy still works fine and Ive tried taking the default.bind from the new starter.fps but no luck

Any ideas anyone?