It's all about your breathing.
On a plane, as you descend into a windy area and the captain tries to keep things nice and steady in a storm, you might start holding your breath before you ever realize it. If you pay attention to your own breathing, the more you get stressed out, the more you take short breaths or even stop breathing for short periods.
Honestly, you might have good reason to be a little alarmed as the plane seems to take rollercoaster-like dips. And yet, the hard truth of life is that even in stressful situations there is absolutely nothing you can do about it. (They won't let you into the cabin to give the airline caption any tips.) You are going to have to figure out some alternative coping mechanisms (which applies to much more than just stressful travel).
Here's one I've tried a few times. It's not fancy at all, and you may already have a breathing routine you like. My problem with a few other techniques is you look kind of dumb taking a huge deep breath and holding it, or using some other pattern. So I do something a little different that is not as noticeable to those around me.
If you half-pretend you're going to sneeze, breathing in several times in short bursts as though you just smelled something funny or you just really want to clear up the old synapses (and sinuses), just breathe in through the nose about 4-5 times in a row. This has the exact same effect as doing a deep breathing exercise, because as you breathe in a few times, you're causing your body to relax and you're going to have to exhale longer than usual. Your shoulders will drop, you'll feel at ease, and yet no one around you will really notice.
Of course, there are a few variations. You can try breathing in only two or three times, or see if you can breathe in up to six times or so in succession. (Hey, if it is a really long flight you're going to need something to do anyway.) No matter how you do the breathing trick, you will definitely find that you get into more of a relaxed state, exhaling enough to cause your stomach to push out a bit and forget at least for a few moments about the turbulence, the stress of taking off and landing, or dealing with the fact that the guy next to you is obnoxious.
You can also try this technique in almost any circumstance. No need to pull out the yoga mat or hold your breath for long periods so everyone around you knows what you're doing. That can actually add to your stress if you feel like people are noticing you're stressed out.
The fun part is that you don't really need to worry too much about how often you do this. You can try it just once on a flight which at least gives you the sense that you have actually exhibited a little control over the situation and done something to relieve the pressure. Or you can try it for the entire take-off until you feel more relaxed.
If you try this technique or have ideas on one that has worked for you, no matter how simple, send me a quick note with the tip. I'll do a follow-up article with more ideas.