Certainly not for short hops, but if regular aviation is any indication, it’s more efficient even if you don’t even reach cruising altitude before beginning to

Certainly not for short hops, but if regular aviation is any indication, it’s more efficient even if you don’t even reach cruising altitude before beginning to descend, so I’d imagine any flight that currently is around 4 hours or more would potentially benefit. (Given full technology maturity) that said, we are a long, long way from having efficient engines for that wide of a speed envelope.