An enemy that can put 3 out of 4 airplanes on target in a single morning (plus the persistent rumors of who knows how many groups of swarthy men just walking away from their abruptly grounded airplanes and luggage and quietly melting away) can certainly simultaneously hit any number of checkpoints.
That would be a bad day, or as an opponent would call it a "Perfect Day"...
Think also of the symbolic value for Jihadists if they could inflict mass casualties on Americans by conducting an attack specifically on the location that exists to supposedly protect Americans from them.
What better propaganda victory could they have than by showing there is no safety from Allah’s army by killing hundreds of innocent American civilians who were meandering through the security maze at a major airport?