More from the article ...

... Trump told reporters it would be "stupid" not to accept Qatar's gesture. The plane is expected to be used as a temporary Air Force One, with ownership transferring to his presidential library foundation after his term -- an highly unusual arrangement already raising legal and ethical questions about accepting such a valuable gift from a foreign power.

Equally alarming, security experts warn that retrofitting a foreign-owned aircraft to meet presidential standards would be massively expensive, time-consuming, and potentially disruptive to the already-behind Boeing replacement program. ...

The current VC-25s aren't just repainted 747s. They're a pair of flying fortresses that must be capable of allowing the president to run the country, survive wartime conditions (even nuclear), and be totally secure from outside influence or intrusion.

While the precise details of the current airframe are a tightly guarded secret, some details are included on government fact sheets or have been revealed in various media reports.

The hull is known to be armored, at least, and the windows are also thicker than you'd find on a normal flight. The government would also need to build in weapons systems, like the chaff rockets used against radar-guided missiles, flares against heat seekers, and AN/ALQ-204 Matador Infrared Countermeasure systems, or similar to try and confuse incoming missiles.

Next up, the engines and electrical systems would have to be replaced. The electronics in the current VC-25s are hardened as much as possible against an electromagnetic pulse that would be generated by a nuclear detonation. There are also claims that the aircraft have extra shielding in the engines to help against missile fragments should a physical attack happen.

Next up are communications. Air Force One has air-to-ground, air-to-air, and satellite comms systems that are thought to be the equal of what's in the White House. There are at least two separate internal phone systems - one open and the other highly secure - that would need to be installed and checked as well.

Then there are incidentals. Contrary to what films will tell you, there is no escape capsule on the current Air Force One, nor a rear parachute ramp, but there is a medical suite with emergency equipment and space for a physician which would already need to be installed, as well as a secured cargo area designed to prevent tampering or unauthorized access.
Internal security could be just as bad - or worse

There's a well-documented history of foreign adversaries embedding surveillance devices into physical infrastructure. ...