The whole ship comparison and the easy link between the void between planets and the ocean (between continents) makes comparisons to the Navy and its offshoot (the Marines) more sensible than the airforce. I have to say thought that B5 did not really use a Naval system all the time - There were many Colonels and Generals in Earthforce. In fact, I don't think any high level officers were ever called Admirals, they were always Generals. There were also Sergeants, not Warrant officers or Petty officers.