Because they'd lose their deposit if it wasn't returned in good shape.
Although I wrote this tongue in cheek - it is probably contains a kernel of truth.
If nothing else, these islamic terrorists are cheap (except regarding human life). Remember the first WTC truck bombers? They got caught while trying to reclaim their deposit on the truck they used for the bombing. It must be genetic. Cheap bastards probably only budgeted ten grand to get a plane.
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