Shed - in this post and your previous post (re London) you insist on using the currency of 'departures' to measure performance. The correct measure is 'seats'.
e.g. total number of seats is available from MAN is approx. 250,000 higher in total for S15 vs S14.
e.g. Ryanair adding 170,000 seats compared to last summer (yet you describe this as "plateauing").
e.g. total number of seats offered by BA to LHR in S15 is approx 550,000 (vs. 390,000 by KLM for example)