If we are looking for ways to burn less fuel high in the atmosphere, perhaps there are other ways to fly. The Focus 21 France relies on the "ground effect", where drag is significantly reduced when flying between 1-1/2 and 2 times the wingspan of the craft; fuel use could be reduced up to 40%. All the benefits of flying without the racking, stacking and packing. The Focus 21 is designed for a modest 15 passengers, primarily as a high end yacht tender, but in the cold war the Russians used them for a lot more. ::Dvice
The Russians built a range of ground effect vehicles called ekranoplans. According to Wikipedia:
Ground effect vehicles (GEV) fly above any flat surface, with the height above ground dependent upon the size of the vehicle. Ekranoplan design was conceived by revolutionary Soviet engineer Rostislav Alexeev.
During the Cold War, ekranoplans were sighted for years on the Caspian Sea as huge, fast-moving objects. The name Caspian Sea Monster was given by US intelligence operatives who had spotted the huge vehicle, which looked like an airplane with the outer halves of the wings removed. After the end of the Cold War, the "monster" was revealed to be one of several Soviet military designs meant to fly only a few meters above water, saving energy and staying below enemy radar.
Lun class, photo A. Beyaev
The ekranoplan has a lifting power of 1,000 tonnes, among the largest ever achieved. The KM, as the Caspian Sea Monster was known in the top secret Soviet military development program, was over 100 m long (330 ft), weighed 540 tonnes fully loaded, and could travel over 400 km/h (250 mi/h), mere meters above the surface of the water. . Another model was the Lun-class, entering service with the Black Sea Fleet in 1987; the Lun-class vehicles had a top speed of 550 knots.
Two Orlyonoks in in ground effect cruise
Given the fuel savings, it might be time to pull those out of mothballs and put them back to work!
People are still designing these things...
here is a 19 second movie of "The Caspian Sea Monster is probably the most famous Ekranoplan. It is also the biggest and fastest ever. In this movie, a very interesting take-off sequence where one can see the PAR system (thrust + flaps) and the high pitch used for getting out of the water." UPDATE: yikes, youtube found a whole pile of videos of it!