Long haul flights are a drain on anyone and sub orbital or even orbital flights seem to be the solution to making them a thing of the past. However, such flight isn’t easy, and even one of the most advanced projects being spearheaded by Virgin Galactic requires two crafts to get you high enough to cut flight time.
However, work being done in the UK by Reaction Engines could revolutionize air travel for everyone. It is currently testing the Sabre engine, which is a hybrid engine that can switch from typical jet propulsion to a rocket mode during flight. This means the associated spaceplane they will be attached to, called the Skylon, will be able to take off and land like a typical passenger jet, but is capable of orbital flight by switching over to rocket mode. The fuel is a hydrogen oxygen mix, and the promised flight times will never exceed 4 hours, regardless of where you want to travel around the world.