Charlie calls Maverick "Lieutenant" several times. If you pay attention to Maverick's uniform when they're in various classes, look at his collar brass...he's wearing Captain's Bars (2 Bars). Lieutenants have only 1 bar...such as what Goose wears.

Correction for this entry.

Actually, Navy Lieutenants have two bars and a Navy Captain has an eagle. U.S. Navy ranking is different from the other branches. LT. Mitchell has the correct insignia on his uniforms.