D&D 5E Do you allow flighted Player characters to carry other Player characters?

[Kurotowa]

Provided they are not more than one size larger, are not over their carrying capacity and the person carrying has a free hand. That would be a grapple and all the rules for grappling would apply (the one being carried could intentionally fail the check).

That is really clever and something I'll happily steal. An uncontested grapple on the carried target, meaning the flier moves at half Speed (unless they have the Grappler feat) and the carried PC has Disadvantage when attacking. That seems reasonably balanced to me, and works well with the existing rules.

My current PC just got Winged Boots, and I'm going to preemptively run this idea by my GM so we're in agreement before the situation comes up in game.