Well, they say that it could have flown for six hours after they lost it.
Six hours from Boston (or, well, New York if you insist) to the east is London, to the west is San Francisco, to the south is Venezuela, and to the north is northern Greenland. They're trying to search an area as large as Venezuela to the Arctic circle and London to San Francisco. That's a pretty big area.
Six hours from Boston (or, well, New York if you insist) to the east is London, to the west is San Francisco, to the south is Venezuela, and to the north is northern Greenland. They're trying to search an area as large as Venezuela to the Arctic circle and London to San Francisco. That's a pretty big area.