Originally Posted by
Boslandew
Jet aircraft fly as high as possible for the best fuel economy. As trip distances decrease there must come a point when the shorter distance makes it uneconomical to climb to cruise at FL350 plus. Is there a formula/accepted practice that determines the best altitude to fly over any distance less than the minimum required to make flight at FL350 economical? I'd appreciate any details.
To be honest, pilots have limited formula for this today. Usually it is calculated either automatically by the flight planning system (and is on the OFP) not only for optimum fuel economy, but also other operational things like airspace structure, ATC overload etc. And then there is the FMC which gives us an optimum level as well, however sometimes questionable ones.
That said, apparently the best fuel economy is by flying a parabola, get up as high as possible and then idle the rest of the way down, I've seen cruised durations measured nearly in seconds, not minutes on very short sectors, but single digit minutes are quite common on those short ones.