Are you a smoker? Remember that CATSA no longer removes prohibited items from passengers' bags. You would be amazed at how many times a lighter is in someone's checked luggage (people still think they can put one in their bag). The bag is pulled aside at screening and then CATSA waits for someone from the airline to come and observe the issue and then take the lighter away. So this can take awhile to sort out and the bag misses the flight.

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