why does a flight from grenada to london take twice as long as a flight from london to grenada?

Answer 1

Winds can also affect the flight time. I get 10 hours 36 minutes for a direct flight from London to Grenada and 10 hours even for the return leg. You can get any flight time estimates at: http://www.jets.com/

Answer 2

The flight itself doesnt take twice as long. Its because of the time change. When you fly from East to West you change time zones, so the flight looks shorter on paper. When you return the same happens, but in reverse. If you check the actual hours the flight is in the air, you will find it will be much closer, though tail winds will make somewhat of a difference.