The Department of Defense formally accepted a luxury Boeing 747 jumbo jet from Qatar for President Donald Trump’s use as Air Force One, Pentagon spokesman Sean Parnell said in a statement on Wednesday.

Parnell said Secretary of Defense Pete Hegseth accepted the jet “in accordance with all federal rules and regulations” and that the Defense Department would “work to ensure proper security measures and functional-mission requirements are considered for an aircraft used to transport the President of the United States.”

The jet will require extensive modifications and security enhancements to be used as Air Force One, which must operate as a mobile command center for the president. Aviation experts estimate the upgrades could cost over $1 billion.

Air Force Secretary Troy Meink said in a Senate Armed Services Committee meeting on Tuesday that the Air Force has already begun exploring the extent of the upgrades required and that he would warn Trump and Hegseth should any concerns arise about the Air Force’s ability to ensure the plane is secure enough.

The Air Force said in a statement to Defense News that it currently has no information about its timeline for modifying the plane.

At a value of $400 million, the jet is one of the most expensive gifts given to a U.S. president. Experts and lawmakers have raised concerns of the transfer potentially violating the Constitution’s anti-bribery emoluments clause.