For dropping troops, you can land anywhere to recieve credit. A good landing at runway, hanger will give you a 1.25 multiplier.
Technically speaking there is no speed limit for troops, you can be 400 mph or 100, you do need that 800 feet above ground for the chutes to open.
OR you can land next to the city, come to a full stop, and let em run. (is often faster)
On resupply, it has to come from a diff field.
Drop em on a runway, or hanger pad.