If you wanted non-ploppable air, you'd probably have to raise the lab's cost up to 1000 to prevent a plop-reclaim-airfac start. The cost wouldn't prevent you from pulling out an air-lab at an appropriate time as a second (or third) fac, but would discourage rushing it at the start in a teamgame.
But that would leave a big question about what to do with gunships, because
nobody would build a 1000-cost gunship lab except for vindicators to ship striders/heavies around.