Although there have been numerous instances of passengers having to take over for an incapcitated pilot on a small plane and successfully landing (in the sense everyone survived and/or walked away - it isn’t unusual for the airplane to get damaged), to the best of my knowledge there has never been an instance of a passenger taking over on a commercial airliner.
There’s probably several reasons for this.[list=1]
[li]Commercial airliners carry more than one pilot, in part so that if one does become incapacitated you don’t face that problem, and additional precautions like the two (or more) pilots not eating the same meal (just in case the chicken salad went bad) are taken.[/li]
[li]Airline pilots must undergo a pretty comprehensive physical every six months, which means as a whole they tend to be healthier than the passengers. There have been instances of sudden illness or death in a pilot while on duty but it’s extremely rare, much rarer than in the general population.[/li]
[li]It’s pretty darn rare there’s a serious problem of any sort on an airliner. When it happens you hear about it thanks to the media, but really, on average it IS the safest form of transportation ever devised.[/li]
[li]Anything that’s going to be drastic enough to take out all the pilots at once is likely to take out the passengers, too. The Payne Stewart jet, for instance, depressurized and incapacitated everyone, not just the guys up front. So whether a passenger could have taken over at that point was moot.[/li][/list=1]It is possible that a passenger tried to take over on Flight 93 on September 11, but we’ll never know for sure.
I don’t think there’s a standard way of handling that specifically on an airliner. In a small plane the standard procedure, assuming the passenger is calm enough to be coherent and is able to use the radio to communicate, is to “talk them down”. Someone on the ground would briefly tell them what they need to know to direct the airplane, perhaps have them fly straight and level then do a few gentle turns to get their confidence up, then take them step by step through getting the airplane down. Most small planes have very similar procedures for doing this, and they tend to be forgiving of less-than-perfect performance. Passenger jets, however, are much much more complicated, require a higher level of skill, and slightly different skills to land safely. And they are less inclined to forgive an inept pilot.
However, if events conspired to put a passenger at the controls of a big jet, presumably they’d attempt the same - someone on the ground famillar with that type of jet would attempt to take the person step by step through the landing procedure. Like, there’s an alternative?
Would it make a difference if the hypothetical passenger was a small plane pilot? Tests on simulators of this very suggestion have demonstrated that a piston-engine airplane pilot tend to do no better than Joe Non-Pilot in such circumstances. This was sort of surprising to all concerned, but apparently there is sufficient difference between small planes and really big people-haulers that knowing how to safely fly a piston single or twin is not going to help you much, if at all. Might make it easier for you to find the radio and use it.
This sceanario was used in the movie Executive Decision, Kurt Russell, who plays the lead, happens to be a small plane pilot of considerable experience and actually paid for some jet simulator time to see if he actually would be able to handle it. He couldn’t. Crashed every time.
On the other hand, if you really DID find yourself in such a situation you’d be very highly motivated to make it work, and that might give you an edge you wouldn’t have in a simulator where you know, no matter what, you aren’t really going to die.