I'm so glad to see this topic discussed. I should have brought it up in 2022 when I took my first plane ride after contracting COVID in 2020. I was diagnosed with Long COVID. I have been getting better - longer periods of time between what I call "episodes." I took my first plane ride after COVID in November 2022. After the end of each flight, I could hardly make it up the gangway. My shortness of breath, dizziness, feelings of disorientation, weak legs, blurry eyes were scary. Luckily, for the November round trip flights, my husband was with me. He flagged down rides for our connecting flights. I never would have made it on my own. I flew alone to CA in March and I got wheelchairs for connecting flights and at my destination. I never would have made it on my own. All I can guess is that the change of altitude brought on my symptoms. Of course, like many of us, my pulmonary tests are normal
Anyone had any other explanations?

Everyone's symptoms are so different and their triggers are different. I didn't have any trouble with the flying, for me it's the physical exertion that triggers my symptoms. I canceled an international trip a couple months ago because I knew I couldn't handle all the walking and standing. Sounds like other people have had trouble with flying so maybe discuss it with your doctor first? Warm wishes to you -- I hope you're able to go on the trip and that it goes well if you do.