These are all hallmarks of secret, unannounced trips made by American presidents to war zones and high-risk areas, a decades-old practice that has drawn new scrutiny after President Donald Trump sneaked off ​the regular Air Force One jet to take a separate plane as he left Turkey on July 8.

The protocol has been that staff ‌and members of the press pool accompanying the president were told in advance about the trips and sworn to secrecy. They could opt out if they wished.

A source briefed on the Trump trip said that was not done on this occasion because of the unprecedented nature of the imminent threat facing the president.

Only a small group of officials was aware of the elaborate operation to transfer ​Trump from the presidential jet to a smaller government plane using a catering truck. Most of those left aboard, including cabinet officials and traveling press, were unaware ​that the plane they were on was a decoy under threat of a missile attack.

Here is a look at some ⁠of the secret trips that presidents have made in the past.

BAGHDAD FOR THANKSGIVING 2003

Free-range turkey, corn-bread dressing, Prairie Chapel pecan pie — these were all items on the menu ​published by the White House for President George W. Bush for his Thanksgiving dinner in November 2003 at his Crawford, Texas, ranch.

But Bush was not there to enjoy the ​meal. Wearing a ballcap pulled low, he secretly flew aboard Air Force One to Joint Base Andrews near Washington, leaving behind a large press contingent dedicated to covering his every move. The cover story for moving the plane was that it needed maintenance.

The plane taxied into the Air Force One hangar at Andrews, and Bush bounded aboard another plane that took off for Baghdad with ​lights turned off and window shades shut. Plane personnel took reporters' electronic devices temporarily to prevent leaks.

On board were several staffers and members of a 13-person press ​pool who had been told about the trip a few days earlier and warned that if word of it leaked the plane would be turned around in midflight.

The trip did not leak.

Bush ‌spent time ⁠with troops at a U.S. base in Baghdad. Reporters were finally allowed to report the news once Air Force One was on the way home and out of harm's way.

BILL CLINTON SWITCHED PLANES FROM INDIA TO PAKISTAN

In 2000, President Bill Clinton was on a trip to India and Pakistan and was scheduled to fly Air Force One from Mumbai to Islamabad to meet with General Pervez Musharraf, who had taken power in a coup in Pakistan the year before. Security concerns about the trip arose amid ​tensions in U.S.-Pakistan relations.

A pool report from ​that day said Clinton stepped around ⁠the nose of a giant C-17 and proceeded to a pair of small military jets parked on the other side. The first was an unmarked white jet; the one behind had Air Force One's usual USA markings. Clinton was seen boarding the white ​jet, which he took to Islamabad.

OBAMA'S SURPRISE TRIP TO AFGHANISTAN

Many of the presidential trips were taken simply to thank troops ​in war zones.

On Memorial ⁠Day in 2014, President Barack Obama made a surprise trip to Bagram air base in Afghanistan, his fourth such trip there. The trip had been in the planning for several weeks and was kept secret for security reasons until his arrival. The White House put together a small press pool for the trip just a couple of days before Obama ⁠departed.

The president, ​wearing an Air Force One bomber jacket, seemed to relish the surprise, telling 3,000 troops he had ​been in the neighborhood and "thought I'd drop by."

TRUMP GOES TO IRAQ

At Christmas time in 2018, Trump and his wife, Melania, made a surprise visit to U.S. troops in Iraq. It was his first trip to ​a conflict zone nearly two years into his first term and days after announcing a pullout of American troops from neighboring Syria.