Coming in the next unstable will be the ability to produce units like that. There are two new properties (isAirTransportable and isAirTransport) that will facilitate it. The reason they're tagged to air transports is simply to differentiate them from naval transports. For naval tansports, transported units are moved into the sea zone to load, but for the new transport type, they will be loaded from non-moved units that start in the same territory. It's a subtle difference, but pretty important in the code (and a bit of a PITA).
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