由香港到世界各大城市的飛行時數?

Hi, you can try this website http://www.airrouting.com/content/tdcalc.html and it calculates the time and distance between two airports for you. Unless you know the code of the airport (e.g. LHR for London Heathrow) you can type the name in the 'Airport Locator' tab on top of the website and you will be given the code ga la.

Hope this helps... :)