Choose New Airbase

[Krasny]

i just built a tank in a city with an airbase, and noticed the airlift button appeared, on the tooltip it say 'airlift t / choose new airbase shift+t'

why do tanks need airbases? and why should they want to choose a new one?

any ideas?

[vmxa1]

It is a mechanism to let you move troops from one city to another.
Any city with an airport can have units lifted to it. Yu can only do one unit per turn, but an airport can recieve an unlimited number.

This is a very good way to reenforce a beachhead. Bring a settler
build a city and rush an airport. No have every airport lift a unti to that city and run over someone.