Certification efforts took Boeing Test & Evaluation flight crews around the world to satisfy the thousands of certification requirements including extreme tests for conditions the 747-8F will never experience in service. Crews also flew long distances, with some more than 13 hours nonstop, to achieve test conditions. Two such examples were the million pound takeoff -- the heaviest in Boeing's history -- and the higher-density loads test, requested by launch customer Cargolux, which was more than four times the FAA required amount.