Aer Lingus and British Midlands flights between Heathrow Airport and Dublin were disrupted last night as a British Airways 747 aircraft became stuck on a grass verge as it taxied to a stand. Some flights were cancelled while others were rescheduled. The northern runway at Heathrow, which handles 600 flights a day, was shut as a security measure following the incident involving the aircraft which arrived from Boston at 7.40 p.m., an airport spokesman said. Four ambulances were dispatched, but all 130 passengers got off safely. The spokesman said some delays occurred while it was being towed away.