It’s not just that US authorities had him on the radar but his FATHER reportedly warned authorities. It is absolutely absurd for Napolitano to claim “the system worked” when he actually got on a plane with explosives and it was his fellow passengers, not officials, that resolved the situation.
The “knives-with-blades-smaller-than-three-inches-are-OK-because-who-could-use-one-of-them-to-hijack-an-airliner” system worked well about 8 years ago too!