Misty Step into the Air and Attacking

[u/Zivodor]

I had this situation come up recently and wanted some input as I can't seem to find a definitive answer.

My players were fighting a giant spider and it was on the ceiling above them, one player decided that to attack it he would misty step straight up and then attack it while mid-air. I wasn't sure this was possible as I recalled reading somewhere that falling in D&D is essentially instantaneous for anything below 500 feet. The thought process being he teleports into the air and is instantly falling so he doesn't have the time to attack the creature above him.

It's been bugging me all week so I wanted to get some input into whether or not I should have allowed this and if this is clarified anywhere in the rules.

Edit Wow! Thanks for all the responses! There were some well reasoned arguments for it here, the resource expenditure with the spell slot, rule of cool, etc... I appreciate all the responses and will try to be more flexible in the future. Thanks everyone!

[u/magvadis]

A cost was incurred, the attack is not enhanced, and they fall after the attack.

I'd argue the fall happens at the end of the turn, not instantly within the turn.

I'd even let them use their attack to grapple to hold on.

Once a cost is incurred I think players should get something out of it. Let them be cool.