cwl4eva - now that you say it it does look a tad patchy especially on some days where it looks like only 2 a/c are needed for the timetable.
E.g on Mondays (just looked at a random week in November) EDI, BFS, AMS, GLA and AGP are the only routes served and these can be completed with 2 a/c. The same goes for Thursday where the timetable is sufficient for 2 a/c to complete. Not only on these days but if you look at Tuesdays and Wednesdays it still looks a little light with long gaps between different routes one as long as 18 hours I recall!
Don't get me wrong I'm no expert in these things but it seems very strange to have one a/c lying there all day especially with a low-cost model - it does seem inefficient to say the least!