In aircrafts ( jets ) space is bound to pitch up and cannot be unbound

Jump into a custom server that has jets. Bind pitch down to something else (I used Left Alt since people were talking about it). Jumped into the aircraft to verify my bind for space bar being primary fire was working and not pitching the aircraft.

Then I rebound pitch down to my arrow key and it resolved the issue.  Space was no longer bound to pitch down as well.