When you fly it is important to coordinate your sleep schedule with your destination while en-route. This is harder to do on short flights. Also picking the right flight time is critical. Horrible jet lag is due to poor sleep in the plane, dehydration due to the dry air in the cabin, and non-adjusted body clocks. The latter can easily be fixed.
Lets say you travel from NYC to London. To minimize jet lag on arrival, you want to take an evening flight and sleep the whole way. As soon as you board the plane, set your watch/phone to London time. If you can fall asleep before take-off you are golden. When you land it will be morning and you should wake up better prepared for a new day. You will be tired, but not dead tired. Use caffeine and sunlight liberally to stay awake until your desired bed time. Now you should be well on your way for your body clock adjustments for your stay.
On the return trip from London to NYC, you want to take a morning flight and stay awake. Watch movies or read a book. Again, as soon as you board set your watch/phone to NYC time. You will get tired after dinner, so just force yourself to stay awake until your desired bed time and then get your sleep.
With short flights, you have to start adjusting your body clock a day or two before you leave by going to bed earlier or later depending on the timezone of your destination. So if you are going from NYC to LAX you need to stay up 3 hours later and sleep in 3 hours just before your flight.
For really long flights, like LAX to SYD, set your watch/phone to SYD time and begin following that time for your sleep schedule. Even if you cannot fall asleep, just closing your eyes and relaxing or meditating will help. When it is daytime in SYD, stay awake. Read that book or watch movies.