I am 95% better now. I did fly when my ears were bad. At the time I was trying to wean off the sudafed, since my allergies were improving. I don't know why I did that a few days before a flight!! It was a mistake. I could NOT pop my ears on the descent. Going up was fine. Going down, that hurt! The first thing I did when I landed was head to a pharmacy to buy sudafed and made sure I had it for the return flight.
Be aware that the soft tissues of the nose, sinuses, throat and eustachian tubes can swell from thyroid dysfunction. The thyroid controls everything. Literally. Once I got that under control, most of my allergies, sinus and eustachian tube swelling went away and I was able to go off all of my allergy medications. I had been on Flonase, Zyrtec, Singulair, Mucinex and Sudafed - and all year round, for over ten years. Plus ten years of allergy shots. It turns out, I've probably had a sluggish thyroid off and on during my life. I've been able to get better without thyroid medication, just with vitamins and food.
Thyroid issues can be caused by, and can cause, nutritional deficiencies. For example, you lose the ability to convert beta-carotene from food into vitamin A. I take Vitamin A in the form of retinyl palmitate now, and it has been a key supplement for me for a lot of symptoms.
A month ago, it was so annoying to speak because of how my own voice sounded to me with my blocked ears. I felt like I needed to pop my ears every fifteen seconds. I was feeling really good otherwise. It was my last lingering symptom and I couldn't figure it out. I could pop my ears easily, but they became muffled almost immediately after. It was that my ears seemed to be losing air so fast that I needed to pop them all the time, even though I was just sitting on my couch, not driving up and down mountains.
There is really nothing online about this topic that's helpful. No solutions, or explanations about what causes this or how to fix it. But I finally managed to find some information in veterinary research, of all things, and it talked about vitamin A. I had taken it last Fall, and it helped, but I was nervous about getting too much, so I stopped. I restarted that day about three weeks ago, and felt immediate improvement. During all this time, I've been taking a lot of other vitamins, including sublingual B vitamins which are all important for the soft tissues of the mouth and throat, and eustachian tubes.
Best of luck on your trip!