A airplane stands in the hangar at the European DHL Express air freight hub in Schkeuditz near Leipzig, Germany. This past summer, an incendiary device caused a fire at the cargo facility. A blaze officials are now linking to a wider, Russian-backed plot to target planes headed for Canada and the United States.

Transport Canada quietly changed air cargo importation rules for 55 mostly European countries in September, throwing the system into chaos — all in response to an alleged Russian plot to place firebombs on planes destined for North America.