LONDON — China has recruited as many as 30 retired British military pilots, including some who flew sophisticated fighter jets, to train pilots in the People’s Liberation Army, according to Britain’s Defense Ministry. A senior official said the ministry worried that the practice could threaten British national security. Britain said it was working with allies to try to stop the practice, which the official said dated to before the coronavirus pandemic but had gained momentum in recent months. The recruited British pilots, the senior official said, included former members of…