If you want to fly into a certain city (I will use LHR for example), can you look at fares on Google Flights departing from anywhere else? I can't figure out how, if it is possible. The program always defaults to my regular departure city.

If this were for a domestic US flight it would be easy, but since fares ex-Europe aren't equal to ex-USA it doesn't work in reverse. I would like to look at fares departing from any/all major US cities to LHR on a certain date, and checking each city (or a region) gets to be time consuming.

I searched but couldn't find a thread that talks about how to use Flights. Does one exist?

Thanks