Alcock and Brown's flight was between Newfoundland and Ireland — both of which are islands – whereas the NC-4 flew from Long Island (very close to the mainland) via Massachusetts (on the mainland), Nova Scotia, Newfoundland, and the Azores to the mainland of Europe, in Lisbon, Portugal, assisted in navigation by 21 U.S. Navy warships spaced on the average about 57 nautical miles apart along the route over the open Atlantic Ocean.