Flights at Britain\'s second largest air hub, London\'s Gatwick Airport, were disrupted on Friday when a hot-air balloon strayed into its airspace, a spokeswoman said. Five departing flights were affected after airspace was shut on safety grounds at the airport in Sussex, to the south of London, she said. \"Airspace was shut for safety reasons after a hot-air balloon strayed into the Horsham area,\" the spokeswoman said, adding that the airport reopened at 0820 GMT. Gatwick is the busiest single-runway airport in the world, handling 33 million passengers a year.