...and if the Cessna is carrying a fresh nuclear weapon from North Korea (or soon Iran)...
What a stupid way to deliver that nuke! Could not fit lead shielding in the Cessna nor air scrubbers. Can do so in an SUV -- ANS in an SUV you already have thens of thousands of them in the Beltway. Use some simple logic. Stop the panic, already.
Actually one at the state of development of both nations would be too heavy for this aircraft.