The German operation accounted for just over a quarter of the airline’s $487 million revenues in the six-month period, according to a Turkish Airlines interim presentation.
But it also made net losses of $12.5 million compared with $2.1 million for the main Turkish division of SunExpress.
SunExpress uses 25 Boeing 737-800s for its Turkish arm, plus 28 more aircraft leased from Turkish Airlines, while the German carrier has 15 737-800s.
Turkish Airlines says SunExpress expects to take delivery of 50 single-aisle Boeing aircraft over the 2015-21 period.
Fleet planning schedules for Turkish Airlines itself shows that re-engined types will account for half of the mainline carrier’s single-aisle fleet by 2021.