I was in Berlin some days ago- and witnessed something similar when standing on TXL
's spectator's terrace: quite a few Turkish planes within few hours.
Berlin is the thrid largest Turkish city in the world (after Istanbul and Bursa), the Kreuzberg quarter for instance makes one think that one is beyond the Bosphorus...what I want to say is, there are a lot of immigrants from Turkey in Germany, Belgium and the Netherlands, too.
Amsterdam is probably something like the 6th biggest Turkish city (a wild guess).
And as it is July now, it is the height of the holiday season also - from Zurich alone there are 5 flight to Antalya today (July 15).
Turkish airlines usually, from what I have observed, land always close to each other - I can only speculate, but I think it has to do with slots and an optimized time schedule (three Antalya flight arrive within 45 minutes in ZRH
Our battered suitcases were piled on the sidewalk again; we had longer ways to go. But no matter, the road is life.