Today when I was at the station waiting for a train a Continental 757 passed a few feet overhead on approach to GLA. It had no registration under the wing. American doesn't, I'm sure United didn't either but I think maybe the Northwest D10's did. British and European aircraft have underwing regs so why are they missing on most American ones? Is it a legal requirement in some countries but not the US? It is annoying when you are spotting somewhere where they fly overhead but you cant see the reg. Surely a little bit of paint under the wing wouldn't send anyone broke.