Thanks for the hint, DFire870. The SFBT Construction lots were moved to the airport menu because it was the only one that wasn't overcrowded at the time they were made, and apart from the "Building: Airport" occupant group, they don't carry any airport properties at all, but are merely eye-candy parks. I don't know how exactly Swamper's airport support file works, but considering that most of the modular airport lots are merely eye-candy as well (and only one building, like the tower, has actual airport functions), I don't really see why the construction lots should affect the game, but not the modular airport lots.
Are you a bit familiar with the modding programs, such as the Reader? Open the MML DAT and try to edit the occupant groups in all exemplar files in order to move them back into the park menu by removing the "Building: Airport" occupant group (0x00001508) and adding a "Building: Civic" and "Building: Park" occupant group (0x00001005,0x00001006). Don't remove the "Building: Landmark" occupant group (0x0000150A) from the construction lot, though, since this one is necessary for the MML functionality.