The Department of Homeland Security issued an alert Wednesday to airlines that suspected shoe bombers are plotting to enter the country on an overseas flight.
“It’s a reminder that we are under constant threat and an advisory to airlines to be on their A game,” a source briefed on the threat told NBC News.
The alert contained no information as to which country the flight would originate from, the time of departure or the airline. The vague warning suggested only that recent credible intelligence supported the threat.
Officials have ordered airlines to pay careful attention to passengers’ shoes, and warned travelers to expect increased security pat downs and full body screenings.
"As always DHS continues to adjust security measures to fit an ever-evolving threat environment," a DHS official said.
Another source called the threat moderate.
Homeland Security also warned of a threat involving toothpaste in Sochi just days before the Olympics began, though this new threat is unrelated.