In 1984 a great shoot em up was released for the Arcade by Capcom and that game was 1942. A game in which you shot down enemy planes, avoided being shot out of the sky and performed awesome rolls while collecting power ups. One of the more unusual power ups was being escorted by two other planes in formation that gave you the edge. It was an awesome game and still is today, but thanks to a mention by Zsolt there's a new shoot em up that's appeared on Steam Greenlight that's inspired by that great 1942 game. It's Knights of the Air, a top down 2D/3D shoot em up set into the first world war.
Going by the trailer you'll see the inspirations pretty much straight away, from how the planes react, to the collection of power ups and the three plane formation which featured in 1942. It is certainly looking to be a fun game but the developers will have to be careful as purists may only prefer the original game ;).
Steam Greenlight page