Ah, but that's a little different scenario than I was picturing.
I was imagining a terrorist trying to smuggle explosives on board a plane, getting caught, and then setting off the explosives as a "last ditch attempt" to cause damage. This is a little different than the idea of "coordinated bombing". In that situation the terrorists would be less limited as to explosive size (no need to sneak anything past security, so go nuts with the C4).
And yes, it would cause delays, re-screenings, and horrendous problems for the airport. I still think it would be less problem than if a plane were actually brought down with explosives.