[5] Although improved over afterburning, supercruise generates more noise and offers worse fuel consumption than modern subsonic engines.

A variable nozzle is a practical necessity to control the backpressure and accelerate the mixed exhaust back up to supersonic speed at cruise.

[7] A 55-seat aircraft model was to have been powered by three 15,000–20,000 lbf (67–89 kN) thrust engines without afterburners, with shorter maintenance intervals than subsonic jets.

[7] Intake compression would need a low-pressure core, and derivatives of existing 3–4:1 bypass-ratio turbofans are a compromise between takeoff noise and wave drag, with a good fuel efficiency.

[9] Dave Richardson, of Lockheed Martin's Skunk Works, said that suitable engines with low overall pressure ratio are scarce.