[aphextron]

All long haul commercial aircraft are twin engine now. The 747 is a relic and used almost exclusively for cargo now, and the A380 has ceased production. The game changer was new ultra high bypass engines like the GE90 that made the fuel savings of a twin engine configuration attainable by having sufficient thrust to replace four. Also with increased reliability, ETOPs regulations have allowed for twin engine jets to operate across practically any stretch of water. And with the decentralization of routes, the need for huge 400 passenger planes has gone as well. The future will be entirely twin jet.

[kensai]

The future will hopefully be electric. The amount of engines might rise again.

[jason0597]

Nothing so far electric has come anywhere close to the energy density of kerosene, and given how important it is for planes to be as lightweight as humanly possible, expect kerosene to remain in use for many decades to come. Unless, of course, a revolution occurs in battery technology that makes them more energy dense than kerosene.

[brilee]

A tesla's battery pack is about 1000 pounds. The gasoline that would get a car to travel the same distance weighs about 100 pounds. For long haul, the fuel/battery weight would dominate engine weight, so unfortunately, I don't think planes will be using batteries for a while.

[aphextron]

Electric will absolutely have a role in commercial air travel. It's going to revolutionize inter-city travel that is currently too far to drive comfortably, yet not quite far enough to warrant dealing with a flight by allowing people to hop on a tiny aircraft with minimal security flying out of small airfields. Think routes like SF-LA. But it's never going to replace jet fuel for long haul flights barring unimaginable breakthroughs in battery tech.

[spaceandshit]

If commercial aircraft go electric (which as the other commenter pointed out, won’t be happening for a while), the number of engines would be 0. Electric motors are not the same as gas turbine engines.

[derekp7]

I think you mean there would be no internal combustion engine. According to Oxford, an engine is "a machine with moving parts that converts power into motion". So an electric motor is still an engine.

[spaceandshit]

Ah, I guess you're right. In the aerospace world, engines typically mean one type of device. I stand corrected :)

[semerda]

Actually Qantas still uses QF74 (a 747B) doing non stop routes between SFO & SYD. LA to Sydney is done by A380. Other carriers use 2 engined dreamliners.

[vidanay]

I just flew on a Lufthansa 747 from ORD to FRA two weeks ago.