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.
Suggested correction: "Post", in the Navy, is also used in the same manner as "adjourned" or "dismissed". It could be argued that the Admiral was stating this is the last duty station from which he will "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.
He's had a few promotions in 30 years. In 1986, he was an O-3. In this film, he is an O-6. He hasn't been promoted at the same rate as his peers, for sure, but that's just who he is. He didn't want to be in a position where he couldn't fly anymore. On that note, he's not assigned to a Fighter Squadron at the beginning of the film, but to a test pilot billet - so technically, Phoenix was correct in her thinking if not her choice of words.
Cyclone graduated in 1988. 34 years later, he's an Admiral and air boss. Maverick graduated two years earlier and stayed a Captain for Amelia's entire life, despite having flown missions in Iraq, among other things. Where did all his service time go? The answer is a "dishonorable discharge." He got his service time annulled because of his escapades involving "The Admiral" (Penny's father), "the Other Admiral", and Admiral Cain. He got fired. In the real world, he'd get fired upon.
You are assuming way too much. While it's true that the Navy would likely encourage him to retire long before the events of the new movie, it's spelled out in the film that he hasn't advanced because he wants to keep flying. He's a maverick, plain and simple. If he has to piss off an Admiral to keep from getting promoted to a desk job, he'd do it.
Let me quote what you just said: "it's spelled out in the film that he hasn't advanced!" There you go. Do you know what else has been spelled out in the film? That at 00:25:10 film time, Hangman was the only active-duty pilot in the Navy with a confirmed kill.
