Anyone who has tried it knows flying in formation is far from easy. These guys have been doing it a while with their large scale warbirds. Always a highlight of any RC show here in the UK.
https://www.youtube.com/watch?v=MOrx-uf9kYM
Nice. It is difficult; needs a lot of skill!
Yeah...and some never master it. Not something I can do. My depth perception is terrible.