How do I create In air physics?

I want to create a player movement where, while on the ground, player can move on the axis and accelerate but once airborn, the acceleration halts. Some thing like a bike going off a ramp, while on the ground a person can accelerate by peddling; but while in the air, peddling is insignificant.

Please Help

You can get this effect in any fps walker script, either unity's or the one on unity wiki. If you choose the one on the unity wiki make sure the in air acceleration box is unchecked.