SWISS has announced that they will introduce the 777 on several flights between Zurich and Chicago beginning June 1, 2017. Specifically, the 777 will be assigned to Flight LX008 and LX009 for 6 of the 7 weekly flights. Overall, SWISS will maintain 12 flights per week between ZRH and ORD.
Here is what service will look like beginning June 1:
LX006 and 007 will still fly between ZRH and ORD 5 times a week (not Wednesdays/Fridays). The flights will be operated with A330-300 aircraft.
LX008 and 009 will fly daily and will have the 777 on the route everyday except Tuesdays. The Tuesday flight will be operated by an A330-300.
The 777 is expected to be on LX008/009 until October 28, 2017. I expect that the Airbuses will come back for the winter due to demand decrease.