loadshifta:
Seniority does not mean you have a right to command regardless of ability or talent.
The company does have the ability to invest in those they choose.
(Initial hiring of course)
The F/O with no command abilities will not be upgraded just because his number is up. (Duh)
Instead he will be given a chance to prove himself and his abilities when his number is up.
(If I have to explain it, you will never understand anyway.)
