The lowest max landing weight on a -200 or later 747 is 630,000 lbs. Landing in excess is allowed, the critical factor being sink rate at touchdown, which if more than 300 fpm could cause landing gear collapse or structural breakup. Max landing weight for runway length must also be calculated. If the aircraft weighed 570,000 lbs., the crew knew at the initial takeoff brief they were capable of an immediate return and landing. Assuming there were no deferred maintenance discrepancies, such as an inoperative brake or anti-skid, which penalize max landing weight.