Imagine traveling between New York City and London in less than two hours rather than the current average of seven. That fantasy may not be so unreal if hypersonic aircraft are successfully developed.

“Hypersonic” refers to speeds that exceed five times the speed of sound. While intercontinental ballistic missiles easily reach such speeds, the fastest sustainable speeds achieved to date by aircraft are just over three times the speed of sound (~2,200 mph accounting for altitude).^a