A day of transatlantic air travel look like this.

North Atlantic Tracks (NAT) are trans-Atlantic routes that stretch from the northeast of North America to western Europe across the Atlantic Ocean. They ensure aircraft are separated over the ocean, where there is little radar coverage. These heavily traveled routes are used by aircraft traveling between North America and Europe, flying between the altitudes of 29,000 and 41,000 feet inclusive. Entrance and movement along these tracks is controlled by special Oceanic Center air traffic controllers to maintain separation between airplanes. The primary purpose of these routes is to provide a Minimum Time Route (MTR). They are aligned in such a way as to minimize any head winds and maximize tail winds impact on the aircraft. This results in much more efficiency by reducing fuel burn and flight time. To make such efficiencies possible, the routes are created twice daily to take account of the shifting of the winds aloft and the principal traffic flow, eastward in North America evening and westward twelve hours later.