This one depends on where you’re traveling. For the most part, general advice is to get a good night sleep before you travel. However, I’m also going to offer an alternative.
Obviously, rest is important and if you’re too tired to travel it can be a miserable experience. However, starting 24-48 hours before I’m due to travel, I start resetting my body clock for my destination.
I work out the time difference, my flight time, and the time I’ll arrive, then I tweak my sleep schedule to start shifting my body clock to the new time zone.
If I’m traveling somewhere with a considerable time difference, say 10-14 hours, I often stay up for 24 hours before my flight. This means I’m super tired for my flight, which makes it easier for me to sleep on the airplane.
These long-haul flights usually coordinate with nighttime in my destination. So, when I sleep on the plane, my body clock is already adjusting. This may not work for everyone, but it is what I use to minimize jet lag on long hauls.