Re: Surely it wil average out
It's just the way 'averages' (arithmetic means) work. Consider a 60 mph journey by bike. If you can pedal at 30 mph in a flat calm, you can get there and back (120/30) in 4 hours. Now suppose there's a 10 mph head wind (to be exact, a head wind that slows you down by 10 mph) in one direction (tail wind in the other, of course). So getting there now takes 3 hours (60/20) and getting back takes 1.5 hours (60/40), and your whole journey takes 30 minutes longer.
However, in the real aviation world, as an earlier post suggested, airlines reroute westbound to avoid the jet stream so this simplistic approach is wrong - faster jet streams further reduce travel times eastbound and don't have much effect westbound.
Anecdotal illustration - a flight from Heathrow to New York will usually route out over Liverpool, Ireland and then you won't see any land until Long Island. But I've done the route on a very windy day and ended up going over Greenland (normally only seen on flights to the US west coast) and coming in over the St Lawrence (I could see Quebec City off the starboard side). The flight took an hour or so longer than normal.
Biting the hand that feeds IT
