Ok, that's a great explanation for one route (and can understand it).
But it seems to be a more widespread explanation than that explanation would well explain. For example, I closed out one plane... and then decided not to upgrade it after all. Every single route that plane served (ex-LHR) lost between 2-5k DOP. Now, we know that swapping out planes, you rarely get the same money back in for the same fare, but for all of those routes, I had to drop the fare by up to 50€ to get 100% load factor.
If I'm the only one noticing then maybe it is as you say, and maybe it's a factor of fewer people playing this round and just not the increasing demand which we are used to. But that doesn't mean demand should be dropping across the board? At the start of the game, I could still increase routes with no competition by up to 50€ per day... now I daren't touch them since I know to maintain LF, I'll have to drop my prices.
All very odd!