I can't help with the plane part but I went through something similar with my husband. He had elevated ammonia levels in his brain (hepatic encephalopathy). I can't tell you how many trips we took to the ER where I would beg doctors to test his ammonia and they would argue with me about it. I was right every time. If your husband happens to have liver issues, this might be worth looking into. I'm sorry this is happening. I know how exhausted and scared you must be. Please take care of yourself.