The school bus thing isn't really relevant, if you've been paying attention to the objections expressed by quite a few posters on this topic. The truth is that for most US parents today, other than the child's fear, the objection to a child sitting near an adult stranger when a parent cannot see the child clearly is that there is too much opportunity for inappropriate touching. (I didn't say it was *my* objection, mind you; I don't have any problem at all with my child sitting alone. He's 7, he is a very experienced flyer, and he knows to call the FA if he is uneasy about something.) That reasoning notwithstanding, if the airlines are going to claim that the dominant mandate is safety, I have real issues with accepting the idea that running the risk of separating a fearful 7 yo (or his fearful parent) is the best choice in that regard. Personally, I don't feel that the sit-alone limit needs to be as high as 13, but a lot of people disagree; I was simply pointing out that ranting at the airlines is less effective than going through channels to get it mandated by the FAA.
Honestly, I've flown RyanAir many, many times, and the rule doesn't cause noticable difficulty with flights to European leisure destinations. I really don't think it would cause as much difficulty as y'all seem to think.