Air Force One sits on the tarmac with an airport catering container adjacent to the body of the aircraft in Ankara, Turkey, on July 8. Win McNamee/Getty Images

A specific threat to Air Force One by a shoulder-fired missile emerged on the final day of last month’s NATO summit in Turkey, according to a person familiar with the matter, prompting the scramble among US officials to devise a furtive plan to sneak President Donald Trump out of the country on an alternate jet.

The threat was specific enough that officials feared Trump’s life would be at enormous risk if he flew out of the country on either the legacy Air Force One plane or the Qatar-donated jet that he used to fly to the summit.

The person declined to say where information about the threat originated, but said it was believed to be serious in part because of how specifically the Iranians seemed to know details of Trump’s arrangements in Turkey.

Officials, including from the military and Secret Service, put together the plan to move Trump to another plane to fly out of the country within hours.

Trump, over the course of his final day at the conference, appeared preoccupied with Iranian threats on his life, raising the issue repeatedly with reporters.

CNN reported in the days following the summit that Israel had shared intelligence with the United States that Iran had recently devised a new plan to assassinate Trump.

But some officials at the time cast skepticism on the Israeli intelligence, suggesting the report was viewed — in part — as a piece of a broader Israeli effort to influence Trump’s decision making on Iran.