... but what if the guy just can't hold it together?
(Anybody?)
I was lucky enough to fly with 2 Delta guys (1 furloughed, 1 retired) when I was an "Ink-Dry" CFI. Even with my whole 300 hours, when I flew with them it was "If you see anything you don't think seems right, speak up right then..."
It's always been my opinion that a good FO is one that thinks like a Captain. Meaning, they're always maintaining that SA and ready to take command if need be.
As a retired Horizon Asst Chief Pilot said to me in my interview, "I'm only going to hire you if I think you're going to be ready to take command of a situation. I only hire FO's that are going to become Captains...so that means you had better be ready to think like a Captain. Is that something you can do?"
My only real experience with a Captain "loosing it" was on a flight into LAX in the Q4. It was an early morning flight, Captain's the PF. The wx goes down to nearly CAT III mins when we were about 25 nm's out. SoCal gave us a hold that was really close to our position. I don't know what "triggered" it, but my Captain blew a fuse at that point. Yelling at me "Tell them we're unable, I can't program something that fast!"
After getting a new holding fix from SoCal, he continued to spaz out on me. To the point where I built the hold in my FMS, flipped the AP to where it was driving off of my FMS and told him to relax, take a deep breath and catchup...no reason to get bent out of shape.
He just couldn't get his head on straight and I was started to question if he could fly a CAT III(A) approach at LAX, as the HUD is on the Captain's side and FO's aren't trained to use it. I was seriously considering a diversion to Ontario because he was just not with me in the airplane mentally.
Thankfully the weather came up to CAT I mins and I was able to fly the approach into LAX.
After we parked, he and I had a closed door talk. He ended up calling in sick and flying home. That left me in LAX for 4 hours awaiting a new Captain.
Atleast I got to eat at the In-and-Out burger next to 24R!