High Flyer is an attack used by many fast cars. It is most noticeable with Radical One.
When a fast car/racer like Drifter X and La Vita Crab clash into another car head on, the victim has 20-80% (depending on the car's reliablillity) to be sent flying the other way and takes moderate damage. This sometimes backfires and ends up with the player knocked into a wall instead.
Sometimes, both happen at the same time (victim flies away and the player takes high damage)