Character mistake: The Admiral refers to Top Gun as Maverick's final post. As Maverick is a Naval aviator, it should be referred to as his final duty station. The army uses the term post.
Character mistake: Phoenix says Hangman is the only active-duty pilot in the Navy with a confirmed kill, but she is wrong because Maverick has 3 confirmed kills and is still an active-duty Navy pilot, even though he has been flying test aircraft. (00:25:10)
Suggested correction: She says, "you are looking at the only naval aviator on active duty with a confirmed air-to-air kill." She isn't wrong. Maverick was not an active-duty navy aviator since three years before that moment and would not become one until near the end of the film, i.e, a week later. Second, films are allowed to show characters that make in-universe mistakes. She corrects herself near the end of the film at 1:58:20, saying Maverick is an active-duty navy pilot with five kills.
Maverick is still an active duty Naval aviator the entire time.
People on active duty get promoted based on their service length. In this film, Maverick has not received a promotion for 30 years, and more importantly, has not scored a single aerial kill in 30 years.