Jet lag.
The bane of air travelers.
It can make a mess of your travel plans if you allow it to do so.
What is jet lag? According to Wikipedia, "jet lag, medically referred to as "desynchronosis," is a physiological condition which is a consequence of alterations to circadian rhythms; it is classified as one of the circadian rhythm sleep disorders.
Jet lag results from rapid long-distance transmeridian (east-west or west-east) travel, as on a jet plane.
" To put it simply, jet lag screws up among others, your sleep patterns.
You sleep when you're supposed to be awake and you're awake when you should be sleeping.
The more serious part is that it could last for a few days.
What causes jet lag? Lets say you're flying from London, England, to Sydney, Australia.
That's about a 21 hour flight across 10 time zones.
You arrive in Sydney at 9am the next day.
The problem is your body clock is still tied to London time which is 12noon the previous day.
You have mysteriously lost 1 night's sleep! Now you know why you have this huge urge to go to sleep.
It takes 1 day to recover from a 1 time zone change, so, it should take you 10 days to recover from a London - Sydney flight.
How do you beat jet lag? You don't.
All you can do is try and minimize its effects.
I was once on a crazy marathon air trip from Chicago to Kuala Lumpur (Malaysia) via New York, Anchorage, Seoul (South Korea), Singapore.
Flight time including transits was an amazing 30 hours, not to mention moving cross umpteen time zones.
I still can't remember how long I took to recover from that incredible journey.
Back to the question at hand.
First, sleep as much as you can in the plane.
Second, drink lots of fluids, not including alcohol.
Third (this is the hardest part), try not to sleep when you arrive at your destination except when it is really time to sleep.
Move around at your destination as much as possible and tire yourself out to the point of exhaustion.
Then try to sleep.
Good luck!