Why Britain cannot simply borrow a spare American carrier

Could the United States lend Britain a mothballed aircraft carrier?

No practical candidate exists, and even a Nimitz-class ship would require roughly 5,000 personnel with its air wing compared with no more than about 1,600 aboard a fully loaded Queen Elizabeth-class carrier.

The surviving conventional American carrier candidates are either museum ships or have been scrapped or committed to dismantling. Nuclear carriers cannot be transferred as if they were ordinary reserve hulls. The personnel gap is equally decisive: a Nimitz-class carrier and air wing require about 5,000 to 5,200 people, while Queen Elizabeth's ship, air group, and embarked troops total roughly 1,600 at the high end given here. A borrowed hull would therefore create a crewing and support problem far larger than the Royal Navy's existing carrier model.