Something I was wondering for some time now and didn't find a satisfying answer on google.

- If I'm flying from LHR to the US, which timezone determines whether it's day or night on the plane ?
- How can I determine if my flight is going to be an night flight, and therefore has limited service (on a recent flight from JFK to LHR they called it sleeper service in CW) ? Does such a thing also apply to F ?