Preparations under way for Qatari jet that will be used as Air Force One

Preparations to refit the Qatari jet that will be used as Air Force One are underway, and floor plans or schematics have been seen by senior U.S. officials, CBS News has learned.

Earlier this year, President Trump confirmed that the Qatari royal family was donating a Boeing 747-8 for his use. Valued at $400 million, the jumbo jet is set to be donated to Mr. Trump's presidential library after his term is over.

Mr. Trump, in May, called it a "gift."

"They knew about it because they buy Boeings, they buy a lot of Boeings, and they knew about it, and they said, we would like to do something," Mr. Trump said. "And if we can get a 747 as a contribution to our Defense Department to use during a couple of years while they're building the other ones, I think that was a very nice gesture. Now I could be a stupid person and say, 'Oh no, we don't want a free plane.'"

There are constitutional rules against a president accepting gifts from outside entities, including foreign governments and even members of Congress. Article I of the Constitution prevents any president from accepting a gift or emolument from a "King, Prince, or foreign State," without congressional consent.

In May, Democratic Rep. Ritchie Torres of New York said he sent a letter to the Government Accountability Office urging an investigation into the Trump administration accepting a plane as a gift.

The Washington Post reported on Saturday that the U.S. government and Qatar are expected to finalize the agreement this week.

A source told CBS News in May that the plane needs to be checked for security and spying devices before it is accepted. Renovations that could cost hundreds of millions will need to be done before the plane is ready to be used as Air Force One, the Air Force secretary said last month.

Jennifer Jacobs contributed to this report.