Airplane travel with oxygen: O2 levels drop, any suggestions?

This is definitely a question for your husband's pulmonologist, so that would be where to start.
You also need to know that the FAA and airlines have very specific requirements for traveling with oxygen concentrators, and do not allow O2 tanks.
You will need to have a letter of diagnosis from the doctor, with predicted/estimated volume need. Check the specific airline for requirements.
You will need an approved oxygen concentrator with sufficient battery life for the duration of the longest flight - don't count on being able to plug in. Any vendor should be able to provide a list, and help choose the best one for your needs.
If you travel infrequently, you may want to consider renting one so you don't have to maintain it for just occasional use.
Does this give you an idea of where to start?
Sue

There is another discussion on this same topic that you might want to read through to learn what others have shared.
-- Traveling and flying with oxygen: https://connect.mayoclinic.org/discussion/flying-with-oxygen/

I thought this might also be helpful -- Patient education: Supplemental oxygen on commercial airlines (Beyond the Basics): https://www.uptodate.com/contents/supplemental-oxygen-on-commercial-airlines-beyond-the-basics/print

Thank you and everyone. He put a call in to his doctor on Monday. Still waiting for a return call as to where to start from him. I feel that since he doctors at the VA and locally he gets left behind sometimes.

You said, "I feel that since he doctors at the VA and locally he gets left behind sometimes." I hear that often! There is a lot of problem with communication between doctors in different systems. Especially because there a several electronic recordkeeping systems, that do not necessarily communicate with one another. My friends who have to change networks for different parts of care, or when they seasonally locate, often find they must hand carry information between providers.
I see doctors in two different networks, both using the same software and patient portal, yet I must have 2 different logins to make appointments, see test results, etc. The patient records must be "manually released" after each visit, so the docs in both networks can see them!
Sue

Thank you. He is likely going to have to do that. They both, the NP at the VA and the MD that Mayo has communicated with feel they are the the primary doctor and it gets confusing. He was set for a cardio rehab program, then the VA found out and after the consultation and going to first class, he got told the VA wanted to run their own tests. I don't understand why it has to be so complicated when he has private insurance. But, since the VA provides the CPAP and Oxygen, I imagine that's the problem. Very frustrating.

UPDATE: We traveled this past week for the first time since the mask requirement was lifted and what a huge difference it made in my DH oxygen level. His level remained above 90 the entire time so he didn't need to use his inogen machine. With a mask on (without the machine) it would drop to the 60's and his heart rate would remain about 115 bpm. He always said that if Covid didn't kill him, the mask would. We will keep taking it along with us, but I sure hope the mask mandate stays lifted!

I came across this article if interested Pulmonary Disease and Air travel
https://tripprep.com/library/pulmonary-disease-and-air-travel/traveler-summary

Thank you. There's a lot of things to know when traveling, isn't there? We get the doctor's prescription, Delta's pre-approval (which is done through OxygenToGo) and one trip we had to bring three 16-cell double batteries with us. He only needed one, but the rules are the rules. An agent at MSP suggested we get the TSA pre-approval, which we did. Carrying along his CPAP, hearing aids, Inogen (batteries, not attached), Vibralung, oximeter, BP machine, inhalers, thermometer, meds, etc. is like a portable clinic. LOL
I recently put in an appt request to Mayo for him to be seen by a pulmonologist, since we don't have one around here. We have nothing against his small town doctor or the Veteran's clinic, but I would feel better with another opinion on what we could be doing better.
Your link is a helpful tool. Thanks again!

I am all new to whole o2 levels drop, post covid. I do have pre-existing pulmonary problems, but never had o2 dropping. I am home on o2 and we have upcoming flight in 10 days, so i have been talking to airline, researching which o2 compressor is most optimal as i will also need to use it at night and as needed during the day time. Yes the whole battery hours need to be equivalent to 1.5 times of flight time. So if my flight is 4 hrs, i need to have enough for 6 hrs. We are happen to fly 1st class and i asked, i can use the plug, so need to call back and ask if i still need equivalent amount of batteries. Looks like to even use nebulizer on the plane, needs to be on md letter of necessity along with o2 use. I didnt know that, but this could be airline specific, Aero Mexico we are flying with said they do require.
Thks