Originally Posted by jrl767

1. efficiency relates to capacity (payload, in tons/tonnes) and range as well as fuel burn; the 747 has far more capacity, and likely a bit more range, than the 767
2. just like passenger airlines, the cargo operators are trying really hard to optimize the use of their entire fleet -- esp with air cargo demand soaring
3. several of those all-cargo carriers (Nippon Cargo and Cargolux, at least) only operate 747s, so the question of more efficient aircraft is irrelevant

I would again point you to FlightAware or FlightRadar24 if you want to check in real time

right now the only 4-engine jet in UK airspace that I can see is a UPS 747 en route from their Louisville/SDF hub to Cologne/CGN