How do I make already ride able Gear fly on a double click of the spacebar also?

I Want the birds and dragons in my game able to fly as well as be rideable on the ground. I would like it so that if I hit the spacebar while in the air the pet well fly and if I touch spacebar again It will come back to the ground. And I will do the controls for it. It might be too much to ask but anything helps. Thanks.