How long are the world oil reserves expected to last, going by current consumption. Has there been any research in the area of alternate fuel sources for airliners? With the skies getting busier by the day airline fuel isn't going to last for ever. Hence the need to develop alternate ways to power airplanes is pretty immediate. But the idea of a larger airliner like 777 running on electricity or solar sails seems too bizzare or futuristic. Any comments?