@ FramMaker- Ramjet and scramjet engines are not well suited for passenger aircraft jet engines. They operate at highest efficiency above mach three. Ramjet and scramjet engines cannot self-launch either. They need to be launched by some other of propulsion system like a rocket powered rail launcher.
Jet turbine engines can operate at much lower speeds, and they can launch from a standstill, making them ideal for most commercial applications. They are most efficient at much lower and safer speeds.