A threat that Air Force One could be targeted by a shoulder-fired missile prompted the U.S. Secret Service to secretly move U.S. President Donald Trump onto an unmarked government jet during a ?trip to Turkey last month, a person briefed on the matter said on Wednesday.

The threat emerged on the final day ?of Trump¡¯s ?visit to Ankara for the NATO summit amid heightened tensions with Iran, the source said. The Secret ?Service deemed the threat to be credible and imminent, prompting an extraordinary operation to conceal the U.S. president¡¯s movements. The source declined to say where the intelligence came from but said officials had little time to prepare and devised the plans at the last minute.

Trump ?and a small group of aides used a catering truck to surreptitiously switch them from the big blue-and-white presidential aircraft to a smaller, nondescript C-32A ?jet for the flight out of Turkey on July 8, while Air Force One departed separately carrying senior administration officials, White House staff and the traveling press corps, according to the source.