By Jerry Lawton One of the UK’s busiest airports has become a UFO hotspot following several near misses with passenger jets. A UFO expert has called for the Government to investigate after a string of sights at London Stansted Airport. In one a mystery black craft came within 20 metres of a Ryanair plane travelling at 230mph shortly after it took off. It was one of 27 reported UFO sightings in Essex in the past six years alone. A drone-monitoring system is in place to try and detect such craft, but it did not register, the Daily Star reported. “The pilot saw an object which they describe as bl…