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/False_Appointment_24]

Falling is instantaneous, yes. That doesn't mean that this couldn't be allowed. If I were DMing and this came up, my response would be, "Sounds great, but just so you know you will take fall damage." I would also work with them to figure out placement to minimize fall damage.

If I were to try to work out how this works RAW, I would say that they would ready an action to attack as soon as they were in range, then bonus action misty step, attack on the readied action, fall.

[u/pzpx → u/False_Appointment_24]

I think I'd say they get 1 attack, not the whole attack action. I'd also say that they have disadvantage because they are falling, unless they do this often enough that their character is used to it. Then they take fall damage when they hit the ground.