The rules have also allowed American legacy carriers (United Airlines and Delta Air Lines in particular) to use the Boeing 757 on "long and thin" transatlantic routes between their major hubs and secondary European cities that cannot generate the passenger demand to justify the use of a widebody airliner. The practice has been controversial, because although the 757 has adequate range to cross the Atlantic Ocean comfortably, strong headwinds caused by the jetstream over the winter months can result in westbound flights being declared "minimum fuel", forcing a refuelling stop at Gander, Newfoundland, in order to safely complete their journey.