When we went to Colorado a couple years ago, we were warned to stay to the lower elevations, and to still watch for seizures. Altitude does play a part in seizures. Planes are less of a worry, since the cabins are pressurized for the most part, but can trigger some people.
Prayers that your son can get to baseline once he is at home.
We have a cabin in Big Bear. It is at 6500 ft. Tyler seizes much more in the altitude. I think the thinner air reduces the amount of oxygen to the brain and it brings on seizures. Once we are home, Tyler returns to his baseline.
Yes, even as a child, when we vacationed, I cannot go any higher than a specific altitude - but what my parents did not know was it triggered seizures, but yet, on my end - I did not know how to explain it all, for I loved mountains - always dreamed of going higher and higher.
The other problem was flying - while in specific planes (old planes) while I did not fly alone even though I had piloted them (they were dual pilot, so one could fly when other was unable to) - at specific altitudes; I was gone; not a problem in pressurized cabins.
I never knew I had seized until years into the future (before online came to being) when my Neurologist told me about it .. and to say I always wanted to climb Mt. Everest? To Ski at Lake Tahoe? You can forget about me visiting Denver, Colorado or otherwise I would be ending up in their Hospital.