VivoPerLei

As a passenger - I would take that flight, provided the cost was also half and service remained the same.

sbm12

So still no real meal and squeezed in to 31" pitch for extra time? No, thanks.

airsurfer

No, we should go up, not down to save fuel, I think.

But as modern airplanes are lighter, how possible is it to allow fly higher (40000-50000ft) which requires larger wing surface but the fewer air resistance and less weather problems (like the QZ8501 and AF447 disasters) can outperform the extra weight.

Don't forget, since the beginning of the jet age over 50 years ago we are not flying a foot higher. The 707 has a ceiling of 43000ft nothing less than the 787. It seems that these values (29000-43000ft) are optimized for jet aircraft of the 1960s and not of the 2010s or 2020s.

But that is an assumption.

Proudelitist

In many ways, this is already the case. Except for cutting by half..they have cut times and sacrificed speed for capacity and efficiency. The 727 was FAST. It was great at shortening times between cities..but it was fuel hungry and didn't seat that many people. That simply isn't profitable. If it were, we would all by flying in next gen Concordes today.

Profitability isn't really in speed so much as it is in butts in seats. Nowadays we have horrors like the 757 which jams people in like sardines and increase seat capacity in it's length.

invisible

Well, again, going to thought experiment. Li-Air batteries in theory and people say - in practice as well, could provide energy density of gasoline. But obviously you can't run jet engine on electricity.

So, if in about 15 years it would be possible to fly from coast on electric plane but the top speed most likely will be no more than 300mph. Would it be viable?

But at the same time in 15 years we could get from coast to coast in 10h via HyperLoop...

WHBM

It's actually basic aerodynamics rather than power/fuel consumption of the engines which has led to this relatively constant altitude and speed.

In the cruise, as you go higher, the stall speed of the aircraft in the thinner air also goes up, quite considerably, and you have to keep ahead of this. It's not a huge danger because if speed drops off a bit (eg engine failure), you can just put the nose down and go down.

However if you go a bit faster than the optimum, you start to get additional airframe buffeting. These two limits converge the higher you get. There is a calculated margin, but if you go higher, or faster, or slower, you start to get outside the margin. It varies a bit by aircraft type, but not notably so. Slightly slower jets, such as the BAe146, will not have such a high service ceiling. The point where the two limits converge on a graph drawing these limits is known as "coffin corner". Supersonic aircraft, which have to break through this, need a completely different design.

One of the no-nos of flying is trying to climb up over a weather system. You go round it. There have been several accidents over time from crews trying to climb up over weather which proves to extend higher than expected, they get into turbulence, lose some speed or wing performance, stall, and lose control.

The all-time text book about all this is "Handling the Big Jets" by D P Davies, published in 1967. Davies was the chief test pilot for the UK authorities in the 1950s-60s, and had been central to many of the design details as jets came along, including a well-known stand-off with the US authorities over aspects of the initial Boeing 707, which Davies won and Boeing made modifications.

https://www.flightglobal.com/FlightP...20-%200708.PDF