[mshook]

Concorde engines were actually some of the most efficient ones while cruising above Mach 1.7 (because afterburners were only used to take off and to go transonic until M1.7). So it was efficient but only when flying fast.

Wiki says: The overall thermal efficiency of the engine in supersonic cruising flight (supercruise) was about 43%, which at the time was the highest figure recorded for any normal thermodynamic machine.

https://en.wikipedia.org/wiki/Rolls-Royce/Snecma_Olympus_593

[masklinn]

That's basically all fast flying planes. Engines are designed and tuned for cruising speed, not for going up to cruising speed.

The SR-71 was not exactly manoeuvrable or efficient at low speeds, its efficiency range was above M3.