Fleet Captain

Each starship in the Spacefleet had a Captain. These Captains were largely in charge of the ship and the sailors aboard her, making sure the crew worked together and that the ship remained functional and well cared for. Captains ranked below Vice Admirals and above Commanders.  Captains did not receive orders directly from the Crown, though their orders were still referred to as being from the Crown. Instead, they received orders from a commanding officer who was stationed on Earth or a station orbiting Earth. Some of these orders were passed down directly from the Crown itself, but mostly they came from various other higher-ups who were acting on behalf of the Crown.
It took an average of 18 years from graduation from the Fleet Academy to eventually reach the rank of Captain. There have been a handful of Captains who reached the rank remarkably quickly due to recognition of their deeds. One example is Tyla Martin being given the rank in the year 3243 after she risked her life while saving a member of the Crown. She had been a Lieutenant at the time and went on to end her career as an Admiral.
During the Third Golden Age of Piracy, some people both within and outside of the Spacefleet took some issue with pirate Captains referring to themselves as such. The argument was that while these pirate Captains certainly owned, ran and cared for their own ships, they did not earn them or their title. That anyone who took a ship by force or through any means other than dedicating themselves to the Fleet was not truly a Captain. This was a fringe position to hold and even the people who argued against calling pirates by the title, largely still did so in casual conversation. When everyone, including the wanted alerts, referred to a pirate as 'Captain Peters' or so on, it would be tricky to not follow suit.