Is there a good way to detect if you're midair?

My current method works just fine, but it seems to be inaccurate when used on a laggy server. (I am using a mixture of the motion tag, manually checking if they're in water and the OnGround tag, because the OnGround tag itself is quite... often wrong.) Also, things are much complicated when the player is riding a mount, because the motion tag does not work. (I would grab the mount's motion tag instead but for some reason its always 0? if someone knows how to actually see their motion I would like to know that as well.)
Anyways if someone knows a better way to detect when you're midair it would simplify a lot of things for me, as well as just be nice to know for the future.