Squadron 42 is currently still in development and not avalible to play
Squadron 42 is the singleplayer campaign for Star Citizen. Although they are technically separate games, they share the same law, assets and have also been developed side-by-side.
You take the role of a rookie UEE Navy combat pilot in a single-player epic adventure set in the Star Citizen universe.
Serve aboard a massive Navy capital ship as your custom character interacts and builds relationships with a living, breathing crew.
CIG (Star Citizen and Squadron 42's developers) have been reluctant to share too much information on Squadron 42 in hopes to not spoil the experience, which is why there are few details on what the game is about.
Here's a short list of features which CIG have said are included within Squadron 42.
The cast for Squadron 42 includes some big names which is a promising sign.