Just got back from an overnight vacation to Baltimore. It was a spooky undertaking since I am on O2 24/7 and was scared because I could not take my O2 tanks with me. Instead I had to take a portable concentrator that met airline regulations. It took a lot of fighting to get the right equipment and getting extra battery so I did not run out. With the extra battery I got about 5 hours of O2 on pulse setting instead of continuous flow.
The trip was very successful once everything was in place. The portable O2 concentrator, with the extra battery worked well since the flight was only 2 hours. Unfortunately it was a battle with the concentrator supplier - they sent a power pack that had a plug for the car cigarette lighter but not one to plug into an electric outlet, so they had the overnight shit a new power pack.
I plugged it at the airport while waiting to board the plane. We went from the airport to a nice restaurant, and the restaurant had a table near a plug, so I was able to plug in, recharge the batteries, and use the concentrator at the same time. My doc said it was okay to double up on the breathing meds for a few days, and that helped a great deal !! I slept with the concentrator plugged in at the hotel and it charged while I slept.
We spent about 4 hours at the aquarium before the concentrator started to get too low. Another restaurant for lunch, and they also had a spot to plug in.
The take away from all of this is to make sure you get the 2nd battery - you may have to fight to get it, but it IS available and doubles the life of the concentrator. Make sure you have the equipment delivered at least 3 days before leaving so that if anything isn't right the supplier has time to fix it. And ask everywhere you go for a place to plug in - I was very surprised that the restaurants had one! And be prepared to alter your plans if necessary It IS doable with careful planning!!
I have heard some have had to pay to rent the concentrator - mine was free, but the extra battery was $25.