hour trip from New York  to London, England, and would have to contain approximately two  extra hours worth of fuel for contingency, yet it flies for more  than 13 hours before running out of fuel. An aircraft cannot take  off with that much excess fuel, otherwise it would be way above the  maximum for a safe landing at the destination or alternate airport.  However in the film, the chief air stewardess tries to explain that  the flight is designated as "Heavy" because it contains enough fuel  for the return flight, however this is an incorrect usage of the  term Heavy. Heavy is used after a call sign to denote that an  aircraft is capable of takeoff weights greater 255,000 lbs (115,666  kg) in the US (FAA standards) and 299,828 lbs (136,000 kg) in other  parts of the world (ICAO standards). The Heavy addition reminds the  tower to leave extra time for the next flight landing or taking off  so the turbulence over the runway can clear.