That will depend on your pledge level.
The game is already multiplayer and you currently can meet, fly with and fight people.
Currently not a lot of people have access to the game and thus the server is usually not populated, but if you ask on discord you can get a few guys together for a nice round.
During Alpha and on the planned event weekends a lot more people should be around. I expect the server to be populated regularly during usual play times.
In Beta I hope we'll see a constant playerbase and at least one server constatly able to support a good fight.