I have the Simply Go by Phillips. I’m on 2 liters and have an oxygen concentrator on wheels. I had to put the wheeled device overhead and push my machine as much as I could under the seat in front of me. Yes, they require you to have a window seat so no one is tripping over your machine. I flew baltimore to Myrtle Beach and they ask if I had 3 times the battery. This was southwest and they didn’t ask for a dr note but I had one. I did only use pulse dose to conserve battery and kept checking with my oximeter. Arrange for a wheelchair as airports are a lot of walking and you get priority boarding.
I’m still trying to figure out how to get from Baltimore to Australia if anyone has any ideas? I even thought of multi stops to charge my batteries. Lol

The folks above have provided you with excellent information. From my own experience I used an Inogen portable which has this pulse setting. I didn't need a Dr note but guess that depends on the airline. I used United from Oregon to San Diego. And yes, they want you to have about 2.5 the amount of battery time as the length of the flight. So for my basically 2- 3 hours of flight time I needed 6 hours of battery life. I found at using 3 or 4 liters I was using up more battery than I expected and the large battery was supposed to last 6 hours but bet that was on a 2 liter setting. One plane didn't have an outlet at the seat but the connecting flight did. I was able to recharge somewhat at SFO airport. But I really love my Inogen machine. It was expensive as hell but worth it. I use it for when I do my "laps" in the house for exercise. It has worked beautifully and I would buy it again.

Having only had experience with American Airlines, I can only give my experience with them. I make reservations on line just about every time I fly, but you can do the whole thing at the ticketing counter, too.
Here are the basic, most important things to know;
1. You must have a window seat. No bulkhead seats or emergency door seats either.
2. Airlines have specific brands or types of portables that they will allow you to use. Inogen seems to be their preferred brand, but there are a few others that they accept. Those types can be readily found on their website..
3. Airlines generally require that you have enough battery to last 2 1/2 times the number of hours in your flight. Crazy, right? But they cannot or will not guarantee that you will have access to electrical outlets.
4. Wheelchair requests from departure and arrival ticketing to gate, to baggage claim should also be requested either on line or at ticketing..
5. Finally, keep in mind that the higher the planes' altitude, the more difficult it is to breath. You will probably have to crank up your concentrator at least by one litre, so be sure to have your oximeter handy, to gauge your %.
First time can be intimidating. It becomes old hat after a couple of trips.
Good Luck!😁

I found this information helpful when making air travel decisions.

"What is the cabin pressure on a plane? At cruising altitude, the cabin pressure is between approximately 11 and 12 pounds per square inch (PSI), simulating the pressure we'd experience on a mountain that is between 6,000 to 8,000 feet high."

Since you will be at between 6,000 to 8,000 feet at cruising altitude (compared to your home altitude) you need to make sure that your portable equipment can provide enough O2 at 6,000 to 8,000 feet.. If your portable O2 equipment is sized for you current needs/altitude and does can't provide additional O2 capacity you may need equipment that provides higher output on the plane.

As the previous posts said, check with your doctor and the airline first. You may want to schedule a walking test that simulates 6000 feet (if such a thing exists) and see how much your O2 needs change.

Please share your experience with us. There have been many threads asking similar questions and your feedback would be helpful.