I have a frankly nightmarish build with a lot of reach and a huge bonus to tripping. Then I started wondering about how this build would fare in a fight with an ubercharger. You can trip while flatfooted with Combat Reflexes... but how does that interact with Leap Attack? Can you trip someone while they're jumping? What happens to an airborne tripped character?
Looking at the closest analogy, a flying character can be tripped, and falls as if they hadn't maintained their minimum forward speed (falls 150 ft and takes falling damage if they hit the ground). In this question about tripping flying creatures with good or better maneuverability it came up that:
Creatures that fly without wings (and any creature with perfect maneuverability) can't be tripped while flying.
I don't know whether flying via momentum (i.e. jumping) counts for this, and the source is not RAW (I assume FAQ or similar, but the link was dead). Does it make sense for a jumping character who gets tripped to promptly fall flat on their face? Or would momentum keep them moving forward to their target, and if so would they still be able to attack upon reaching them (presumably taking the -4 penalty for attacking while prone)?