Airborne
Airborne crowd control effects are made up of two components: a movement modifier (called a "move block" by Riot, referring to a chunk of code) and a stun (which is responsible for the disabling to attacking and casting). In the game, the most recent move block will over-rule any previous move blocks.
The target is unable to control movement.
The target remains targetable and will be affected by abilities as if they were on the ground (such as Miasma).
The duration of the effect is related to how long the target is in the air. A common bug where a target who is dashing is made airborne causes them to be knocked "into orbit". The duration is largely extended due to the increased distance the target has to fall.
Interrupts active move blocks, namely other airborne effects and dashes.
Can be interrupted by subsequent move blocks, namely other airborne effects, dashes or blinks.
The duration is unaffected by crowd control reduction.
The effect cannot be removed by cleanse effects.
The target is unable to cast abilities or basic attack.
The duration is affected by crowd control reduction and can be removed by cleansing effects.
Through the use of cleansing effects or tenacity, players can remove the stun and subsequently activate abilities such as Flash or champion-specific dashes to break the airborne's move block.
In some instances, the stun duration is longer than the move block (e.g. Sion's Unstoppable Onslaught), but in most cases they are the same duration. There have been cases in the past where the stun duration was shorter, but this usually lead to bug-like interactions and was later "fixed" (e.g. Azir's Emperor's Divide did not apply any stun at all in the initial charge on the ability, which allowed his enemies to use Flash/dash to supersede the charge's knockback and get over the wall).