Some more details:
1 button in InterCity Transport menu, clicking that button opens the airport GEM panels. Once there you'll find a single menu, that contains all the buildings and airplanes.
Plop what you want and then click on the arrow to finish.
You'll have to be careful not to build unwanted things, since during airport project construction you can't delete things.
You'll find the tarmac plaza with other plazas (since it can't be built if put in gem menu).
There are two things missing before release:
* menu descriptions
* airport props (stairs, trucks...)
No more than two weeks...