Update: The mystery has been solved.

President Trump and the First Lady traveled on Air Force One to Iraq late Tuesday to visit with the troops in what was the president's first such overseas visit as commander-in-chief. The timing of the visit was notable, coming just one week after the departure of Defense Secretary James Mattis who "resigned"/possible was fired over objections to Trump's decision to pull US troops from Syria. Trump also ordered the withdrawal of 7,000 troops from Afghanistan last week.

For security reasons, journalists weren't alerted until hours after Trump landed (hence the speculation about his whereabouts). During the trip, he delivered a speech to the troops and posed for photos.

President Trump and the First Lady traveled to Iraq late on Christmas night to visit with our troops and Senior Military leadership to thank them for their service, their success, and their sacrifice and to wish them a Merry Christmas. pic.twitter.com/s2hntnRwpw — Sarah Sanders (@PressSec) December 26, 2018

The president will return to the US on Thursday to continue negotiations with Democrats after Nancy Pelosi said she would call for a vote on a funding bill on Jan. 3, the day the Dems take over the House.

As the Hill pointed out, Trump was expected to become the first president since George W Bush in 2002 to not visit troops on Christmas before news of his secret trip broke.

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Air Force One has been spotted flying over Yorkshire, England early Wednesday in what appears to be a flight headed towards Turkey, according to WikiLeaks and flight trackers - which later noted that the plane has disappeared.

A Boeing 747 with call sign RCH58 left Joint Base Andrews at approximately midnight Eastern time, and was seen over Hungary at approximately 9:30 a.m. Eastern time.

RCH358 left Joint Base Andrews around 0500 UTC & pinged up on my own receiver here in the UK around 1100 UTC. 🤔 pic.twitter.com/GPTziM8o94 — CivMilAir ✈🎅🎄🐈 (@CivMilAir) December 26, 2018

"The Boeing 747 usually used by Trump for Air Force One is currently moving towards Turkey," tweeted WikiLeaks.

The Boeing 747 usually used by Trump for Air Force One is currently moving towards Turkey. pic.twitter.com/TG5Ndzoyvn — WikiLeaks (@wikileaks) December 26, 2018

The unannounced flight has led to wild speculation, particularly considering the fact that Turkish President Recep Tayyip Erdogan invited President Trump to visit Turkey following the announced US troop withdrawal from Syria.

Why is the plane normally used for Air Force One currently flying over eastern Europe flying towards Turkey / Mid East / Afghanistan? — WikiLeaks (@wikileaks) December 26, 2018

Is Trump on a surprise visit to Afghanistan? Turkey? Flight trackers show that one of two planes used for Air Force One (92-9000/VC-25) using what appears to be a fake HEXCODE of AE47C4, departed Andrews Air Force base at midnight. Transponders changed or disabled near Romania. pic.twitter.com/JtVzEPUoLv — WikiLeaks (@wikileaks) December 26, 2018

Others have speculated that Trump could possibly be on his way to visit troops in Iraq for a belated Christmas.

Sources telling me Trump’s on his way to visit troops—possibly in Iraq. Better late than never. But also a bit troubling that so many folks seem to already know about this if it hasn’t happened already. #OpSec anyone? — Paul (PJ) Rieckhoff (@PaulRieckhoff) December 26, 2018

"Nothing for around 3 hours now on 'RCH358'. Could have landed for fuel, swapped hex codes to another ID, gone out of receiver coverage or simply switched off the transponder," tweeted flight tracker @CivMilAir, which noted that there "was no Marine posted outside the West Wing" today.