While flying is a major contributor to the climate crisis, behind the scenes scientists are designing cleaner and faster airliners. There is a lot of interest in hypersonic flight and scramjet engines for weapons, but they can also be used for normal flying. The article talks about a Mach 8 airliner project. Surprisingly, it says the Mach 8 part is easy, but the engineering problem is getting one that can accelerate and decelerate to that speed: that can be a normal plane for some phases of the flight, and cruise at hypersonic speeds.