[Mr Rogers]

What? You don’t think a 19 year old could command an aircraft carrier, let alone a starship? Whats wrong with you?

You don’t need principles, or life experience, or learning from others. Just be a genius and do everything right at 19...”Babes in Space”!

[corkoman]

You don’t think a 19 year old could command an aircraft carrier, let alone a starship?

In "The Mote in God's Eye" (Larry Niven and Jerry Pournelle) there is a good reason for using very young officers for starship command.

[Joe 6-pack]

"What? You don’t think a 19 year old could command an aircraft carrier, let alone a starship?"

Not that it validates the Star Trek myth, but Nelson commanded a 28 gun frigate at 21 years old.

[ican'tbelieveit]

Mid 20s.