Level 17: Flag Admiral
Level 16: Fleet Admiral
Level 15: Admiral
Level 14: Vice Admiral
Level 13: Rear Admiral
Level 12: Colonel/Commodore (Marine colonels do not apply)
Level 11: Major
Level 10: Captain
Level 9: First Officer
Level 8: Commander
Level 7: Lt. Cmdr.
Level 6: Lieutenant
Level 5: Lieutenant JG
Level 4: Ensign
Level 3: Visiting Ambassadors
Level 2: Crewman
Level 1: Civilians/Visitors
The difference between Commander and First Officer is that the XO of a ship (assuming they are of the rank Commander) has a Level 9 clearance on that ship, but only a Level 8 anywhere else. An exeption is if the XO has a rank lower than Commander. They would then hold Level 9 on the ship of their tenure, but the level of their rank anywhere else. Also, a CO of a ship with a rank of Major or higher, is not constricted byt the Level 10 held by most CO's. They hold the clearance of their rank anywhere they go, unless otherwise directed by Intelligence or an officer of superior rank to the officer in question.