President Trump departed the NATO summit in Turkey earlier this month on the old Air Force One jet — rather than the newer plane donated by Qatar — following a credible threat to the president from Iran and allied proxy groups, U.S. officials told CBS News.

The officials told CBS News that the U.S. detected a credible plot to fire a missile at the plane. Upon receiving the intelligence, the U.S. Secret Service swiftly swapped to a backup strategy. 

The news of threats from Iranian proxies was first reported by The New York Times. 

Mr. Trump flew to the Turkish capital of Ankara on the newly donated Air Force One, a $400 million Boeing 747-8 that the U.S. accepted as a gift from the Qatari government last year and spent months retrofitting to prepare for it to carry the president. But after the summit wrapped up, Mr. Trump flew from Ankara to the United Kingdom in the old Air Force One, before switching back to the newer plane to complete his trip back to the United States.

The swap raised questions about the security of the president's new plane. At the time, CBS News reported that he used the older plane at the suggestion of the Secret Service as a precautionary measure amid the U.S.-Iran war. 

The older planes that serve as Air Force One have laser technology to blind an incoming missile, a system that could misdirect incoming munitions and other diversion technologies, sources familiar with the matter told CBS News earlier this month. It's unclear what systems are aboard the newer Qatari jet.

Earlier this week, the White House said Mr. Trump will continue flying in the older plane while the new 747 gets upgraded.

"The new Air Force One is perfectly safe for the President's travels, but will receive additional upgrades and enhancements in the fall which will take approximately one month to complete," White House press secretary Karoline Leavitt said in a statement to CBS News. "During that time, the President will fly on the old Air Force One."

Mr. Trump told reporters the plane already "has a lot of capability," but will be "maxed out" over the next month.

As the war with Iran ramps back up, the president has acknowledged possible Iranian threats to his safety. Earlier this month, he wrote on Truth Social that 1,000 missiles were "Locked and Loaded" for immediate use if Iran attempts to assassinate him.

"Orders have already been given, and the U.S. Military is ready, willing, and able, for a one year period of time, subject to extension, to completely decimate and destroy all areas of Iran," Mr. Trump wrote.