They can be used on airplanes. The unit has to be one that is FAA approved. I think most,if not all, are approved nowadays. Make sure before you buy one that it is approved. You can get them with output of 3LPM for continuous flow. I have one called OxLife. It is bulky & weighs neary 20# with batteries. The smaller units that you can wear or carry easily do not provide much air. They are supposed to fit under your seat on the plane & mine does. The best thing to do is research POC on line and read all the pros and cons of every unit. Mine has had some problems and it was expensive for me when it broke down while I was away from home. I had to rent a replacement & pay UPS for delivery. When it was repaired it was returned to my home address at no charge. Howeverr the one they sent me to use came without batteries & I had sent mine in for repairs with batteries included. So I had a rough time on the plane ride home. I had to make the journey w/o O2 and did pursed lip breathing but it was hard.