The plane will initially be transferred to the United States Air Force, which will modify the 13-year-old aircraft to meet the U.S. military specifications required for any aircraft used to transport the president of the United States, multiple sources familiar with the proposed arrangement said.

Setting aside intelligence and influence concerns mentioned by others in the thread already, I can’t really see how this is faster than modifying planes already in the US. I mean, it’s a plane with luxury stuff. Surely the issue isn’t putting luxury stuff in the thing, but putting security stuff in.

Hell, if the USAF has to start over from scratch, I’d think that it’d take longer, if anything.

https://thehill.com/homenews/administration/5156686-trump-boeing-air-force-one-delays-frustration/

Trump vents frustration with Boeing over Air Force One delays

President Trump is airing grievances with Boeing over delays in delivering new Air Force One jets, telling Republican governors on Thursday he was “getting a little tired” of the hold up.

“I bought a plane. It’s really two planes, Air Force One. Now if Boeing would build the damn thing it would be nice, too. We don’t build like we used to. We don’t build too fast,” Trump said at a reception for the Republican Governors Association.

Like, I assume that time is Trump’s beef here.

EDIT:

Yeah, this seems to agree with that:

https://www.popsci.com/technology/why-does-air-force-one-take-so-long-to-replace/

Why a private plane isn’t a viable option

President Trump, realizing the pair of new 747-8 planes might not be completed by the time he leaves office, has suggested sidestepping Boeing altogether and modifying a used private jet instead. The suggestion to sidestep Boeing entirely and “convert” a used aircraft could face several challenges, experts said. The extensive modifications required to make such an aircraft capable of functioning as the president’s plane would essentially mean starting from scratch—a process Boeing has already been working through for years. As a result, a converted used jet could potentially take even longer to become airworthy than the two 747-8 models currently in production.

“Honestly, at this point, any changes you make are likely to make it take longer and cost more even if you’re reducing capabilities,” Harrison said.

“It [a converted plane] just wouldn’t be anywhere near as capable as the Air Force Ones we have today,” Aboulafia added.

Not to mention that I kind of wonder what it is that makes the existing, older, aircraft such a problem. Whatever it is has to be something that the Qatari royal plane does. Maybe the existing ones don’t have some sort of fancy convenience? It used to be the norm for leaders to travel on warships, and I suspect that considerably more tradeoffs were made there.