This has been demonstrated by REL's involvement in the European LAPCAT project in which REL's Scimitar engine, a derivative SABRE engine, has been shown to be capable of propelling an aircraft half way around the world in 4.6 hours under realistic air traffic control conditions.

In atmospheric cruise mode, the engines can:

• Be designed for efficient subsonic and hypersonic cruise modes
• Operate independently all the way from zero forward speed on the runway to Mach 5.5 i.e. they do not need assistance from other engines to get up to speed (c.f. scramjets need to be accelerated to Mach 3-4 before they will work)