Not only did we miss all those "obvious red flags", but we missed the much bigger ones. His own father had reported him to the CIA. Umar Farouk Abdulmutallab was banned from entering the UK. British intelligence had informed the US authorities that an Umar Farouk had consorted with a known extremist and that he was intent on jihad.

The fact that he didn't have a warm coat is absolutely irrelevant. We had high-quality intelligence against him but failed to act upon it in any way. We need to worry less about whether someone looks shifty at an airport and worry more about keeping tabs on people who we have strong intelligence on.

It is also worth stating that his attack failed and he was unable to damage anything other than his own groin.