Simulators have been around since WW1; I've got a photo somewhere of a sort of swivel mounted wicker bathtub fitted with a Lewis Gun. A couple of burly blokes bounced Trainees around in the basket as if they were defending a plane. Learning to hit moving targets this way was safer and cheaper than experimenting on Baron von Richthofen.
I suspect it's been technically possible to wholly train pilots on simulators for at least 20 years. They have many advantages such as being able to train pilots to manage fault conditions far too dangerous to try for real, like glide landing an airliner after all the engines have failed.
Ten years ago all the advanced air forces were actively investigating not having pilots at all. What essential function does he perform? In a weapon system the delicate pilot is rather a liability because he can't stand the G-Forces, and requires life support. The man is a problem. To improve manoeuvrability a modern fast jet is aerodynamically unstable to the extent that an unaided human can't keep in the air. Instead the pilot 'flies' a computer system that micromanages the aircraft's control surfaces as necessary to stop it crashing. The pilot is only needed to take command decisions, and with good communications, the pilot might as well be in Wiltshire.
And captured pilots can be the major embarrassment when a military mission goes wrong. In the U2 incident, the Russians didn't reveal Colonel Powers was alive and well until President Eisenhower had committed to denying any and all US involvement, a lie. Only then the soviets put the pilot on TV! (The Soviets were a bunch of hypocrites: Col. Powers was exchanged for Rudolf Abel, a GPU spy caught operating in Brooklyn by the FBI .) Strangely, having a human being invade someone else's airspace is far more politically charged than doing the same job with a drone or satellites.
The need for high performance aircraft waned somewhat with the end of the Soviet cold-war. China appears to be developing an aggressive military stance that may trigger another confrontation, in which case I expect many of the next generation of aircraft will be pilotless. The trend is already evident in the decline of the Flight Engineer: modern aircraft have automated out much of the need to employ one.
Dave