Honestly, I'm suprised I couldn't find this when searching, if this is a repost I'm very sorry and I'll admit to being the worst searcher on ownedcore :<
Usually, when you kick a player off of a flying mount while in the air, they'll get a parachute and fall safely to the ground, although if you disconnect/logout, they'll be kicked off and fall to their deathI've only tested it with the [X-53 Touring Rocket] although I'd assume that this works with any 2 person flying mount.
Happy trolling!