Fearless Tower
Touchdown! Greaser!
Could also have been the Captain....ala JetBlue 'this airplane isn't going to Vegas'. In that case it was the FO who stopped the flight. This copilot was pretty young/junior and may not have questioned the captain until it was too late.Nonsense, if the co-pilot hijacked the plane the passengers would be blissfully unaware that anything was wrong.
Without much more info to narrow things down, almost ANYTHING is possible.