In WWII, “formation flying” was a required study for US Navy pilots.
Still is!
Formation flying is great fun!
But, you MUST be careful!
There are obvious reasons why the military flies in formation to accomplish their missions. This necessitates study and practice. It is just not something that my wife and I are into other than sometimes flying close with friends on “hundred dollar” hamburger missions so we can get some good pictures and video.
But as I mentioned we have neighbors and friends with vintage aircraft who really enjoy that type of flying.