There was an analog flight stimulator used by over 500k pilots which helped, but this was war they accepted extremely high casualty rates and not just from enemy action.
As late as the 1960s, the career death rate for US fighter pilots was about one in five, without any help from an enemy. There's a book, "The Making of an Ex-Astronaut", from someone who made it through astronaut training but then realized they didn't want to take the risk of pilot training in a T-38.
The T-38 jet trainer, first flight in 1959, still in use: 1,189 built, 210 crashes and ejections.
I recently read Masters of the Air, and it said that over 10,000 Americans from the 8th Air Force died over English soil, most from accidents during takeoff and assembling forces.
https://www.nasflmuseum.com/link-trainer.html