Sector Fleet is a sourcebook for all versions of Traveller. Concentrating on the Imperial Navy of the Third Imperium, it presents data on naval operations, procedures and ships for many interstellar powers including the Solomani Confederation, the Julian Protectorate, and the Two Thousand Worlds.

Sector Fleet details the role and organization of an interstellar navy as well as the specifics of shipboard protocol such as command devolution, legal and illegal orders, and how much latitude a starship captain has once underway. Sector Fleet also presents details of the exact composition of an Imperial Sector and Subsector fleet; ship strengths and types, and the vital role played by reserve and Colonial forces in backing up the main strength of the Sector Fleet. The fleets of the entire Spinward Marches are described in this book.