I wouldn't say it's his funeral, you can see Maverick attaching his wings badge onto the coffin, why would he do that if the person dead was ex naval aviator who already earned his badge, and you also have a scene where Mav and Rooster (Goose's kid) get into a fight and other hold them back. My theory would be there was another death at training because Maverick was pushing his students too much, the fight was result of something along the lines of "you killed him/her with reckless flying just like you killed my father" and at the funeral he gives up mentoring at NFWS - gives up his wings. Then he goes to Mojave desert, area51 or wherever and gets to fly that black plane Aurura or...I don't know what it is...