The assumption so far though is that the aircraft is only deployed on one route, to run the return flights back and forth. I would think that most airlines optimise their AUE (is that even an official term?) by utilising it on multiple routes.

Hence the massive backlog and logjam after a bit of snow in Heathrow in December, when like a plane needed for LHR to NRT might actually still be stuck in AMS as it was mean to fly from there to LHR before the LHR to NRT flight a few hours later.

I wonder how many MIT math geniuses have been recruited by airlines over the years to help create an algorithm to maximise use of aircraft across their entire flight schedule