With the exception of last year there have been a couple of Turkish Charters a week during the summer months, but I'm not sure which holiday company it was for. For what ever reason they did not happen last year.
The flights prior to last year were operated by Onur for several years. But prior to Onur, Pegasus operated them.
So I guess if the charterer is using Luton again, they will go with the airline that does the best deal