The Qatari royal family is reportedly set to gift U.S. President Donald Trump a luxury Boeing 747-800 aircraft, estimated to be worth $400 million.

According to sources cited by ABC News and The New York Times, the aircraft, which is 13 years old, will be transferred to the U.S. Air Force and upgraded to meet military specifications for presidential transport. It is expected to be designated as a future Air Force One.

The Qatari royal family, one of the wealthiest in the world with an estimated net worth of $335 billion, is behind the gift—believed to be the most valuable foreign donation ever made to the U.S. government. The move is already drawing scrutiny over its legality and implications.

To preempt legal challenges, Trump’s legal team, including attorney general Pam Bondi and top White House lawyer David Warrington, have reportedly prepared legal documentation asserting that the gift is “legally permissible.”