Even if İ can help one person traveling I am already very happy to have helped out. Me and my daughter always have this problem. For my daughter it is so bad that she is always crying which does not add to a pleasant journey.
We tried everything from slowly blowing air into the middle ear, or chewing sweets or distracting by keeping her talking, it did not hep. This year as I mentioned this before traveling to an ear specialist he told me to take one antihistamine before flying. So what I did was hide one tablet (and they are really tiny!) in the food that comes during the flight. I took one myself to check the result. A miracle, nothing at all, my daughter who knew nothing of the trick, said afterwards she had no pain in her ears. I am so pleased that finally (after 11 years!) we can save her the pain.