I have sever COPD and we travel between Canada and the Philippines twice a year. I have been going back and forth for at least 4 years in this condition and this was the first time I was in some trouble. Between South Korea and Manila I could feel a shortness of O2 in the cabin and checked my saturation levels, Low at 78%. I had no O2 as the costs are prohibitive for me; no concentrator as the one recommended is quite compact in all but price. I took 2 shots Novo-Salbtamol, and 2 shots Symbicort as well as a small shot of Nitro and waited a few minutes , O2 was up to 85%. I was a pilot in a previous life so asked the altitude pressure inside the aircraft and told 10,000 ft. I questioned that number as most international flights are 8000 ft.only to find it was actually slightly higher.
I have found most airlines will rent O2 cylinders but almost cost prohibitive for some of us as they seem to think I need a lot more than I normally take to help their bottom line.
If you have a super insurance company there are machines that will fit in a jacket pocket and run for 6 to 8 hours on a battery. The costs are coming down but still expensive.

Generally your oxygen company will loan you a portable machine for a week or so. You must have enough battery to get to your destination without recharging. Even though you could recharge on a layover. The airlines do carry emergency botlles of xygen. My mothers machne quit working on a united flight and they gave her a couple of bottles until the flight landed.

Hi,I have severe copd for 14 years ,I travel from NY direct to Chile about 12 hrs I use Inogen one G2 with 2 battery of 8 hrs each,and 2 lts but in my return I have a hard time after 7 hrs flight I used a 3 lts,now I am in oxígeno 24/7 also in end stage of copd with 23% of lung function,now I do the same trip with 4 stops,in the airport I use the wheelchair service,before to travel the doctor make me take a test with simulation of plain altitude if I pass he give me the ok to do the trip,in 2 opportunities he denied me because I don’t passed the test.Sorry for my English

Airlines require a letter signed by your doctor saying you're able to operate the concentrator and are healthy enough to travel. You must have enough juice to last 150% of the flight travel time ie if it's a 4 hour flight your machine/batteries must be able to last 6 hours. Southwest did not care what seat I sat in as long as it was not in one of the emergency exit seats. I'm a big guy and always paid extra to sit in those seats, so being 6'5" and 270 pounds, being tucked into one of the other cramped seats with the machine tucked in where your feet should go is very, very uncomfortable! So much so that I haven't used my oxygen the last two times I've flown. Without it you definitely notice some shortness of breath but I concentrate on my breathing and do deep breathing exercises.

I have copd mild I think I still work, but finding it a little harder over the last 12months, I started having chest pains when flying last year too. My GP told me have two puffs of ventolin in the airport before boarding and two again before take off, so far it helps, xx