You are very authoritative and you could very well be right, but I'm am nonetheless still fairly sure that now and then, Kirk is referred to as "the youngest" (or maybe just "one of the youngest"?) people to ever earn the rank of captain up until the time period of TOS. But I realize unless and until I can cite an episode, I am just blathering, and I am therefore not the least bit authoritative.
28?? 7 years out of the academy? Highly unlikley
JustKate:
Well, it is mentioned in the Memory Alpha entry on Captain Kirk that he rose to the rank of captain at 31, then was assigned
Enterprise. However, it doesn't cite an episode. I guess this is extrapolated, as we know from
The Deadly Years that Kirk is 34, which probably means he was in command of Enterprise for six months to a year at the time of
Where No Man Has Gone Before.
Also, in TNG ep Conspiracy, we know Captain Picard, Captain Keel, and Captain Rixx reached captain at young ages, as he says to Captain Scott that she was the youngest Starfleet officer to make captain, "present company included." So she broke whoever held the previous record.
Red Ranger