The greatest threat that any security system faces is complacency. The quiet acquiescence and acceptance of all and any form of strange behaviour because "it's okay we have all been screened." It's not about the sky falling in and terrorists behind every potted plant, it's about vigilance. Strange behaviour could easily be just that, caused by accident or irrationality, it could also be something more.

It is well known that those that would wish to harm our society are careful planners and that they are watchful, actively looking for opportunity. They employ rehearsals and dry runs, practicing for their "spectaculars". Reports are emerging, possibly not true, but time will tell, of ISIS sympathisers employed as baggage handlers etc at Brussels airport, it would be remiss of ISIS not to have agents inside an airport they planned to attack, people who have access to airside and are watchful for opportunity to get something aboard an aircraft, but it's okay because our "enhanced" security is massive overkill.

It may be overkill but the complacent attitude of the frequent flyer with an element of self importance, who has important things to do, for whom security is a PITA and a nuisance is probably the greater threat than the odd seating cock up. Does that mean we should take their view as either worthy or relevant? I go with a captain at MUC who in this situation had the plane de-boarded and re-searched to ensure that nothing had been left behind or tampered with by the errant boarder.