The topic of thinking in advance about what could go wrong, brings me back to my progression of posts about engine failures at take off. In a single-engine aircraft, you have to stop or land, and your choice is where. In a light twin, you have to abort the take-off if the airplane is on the ground, and in flight at low speed you may or may not be able to get the gear up and maintain the speed and altitude to turn back to land on the runway. A pilot must have thought about the options in advance and then maintain airspeed and control in order to have the best chance of at least collecting insurance on what's left of the airplane. This pre-planning becomes formalized for large multi-engined airplanes.
In transport category aircraft, the speeds involved are sufficient that trying to stop with insufficient runway remaining could be as dangerous as trying to fly without sufficient airspeed. To quote Maverick from Top Gun "You don't have time to think. If you think, you're dead." So transport category airplanes are certified and flown in a way that reduces the amount of thinking the pilots have to do at such a critical moment. To begin with, transport category airplanes are required to have enough power to accelerate to take-off speed and fly with one engine failed. And according to the rules for operating them, at any stage of the take-off there is always enough runway to either continue the take-off or to stop on the remaining runway. The speed that determines that go/no-go point is called V1 (vee-one) and is determined and discussed in advance of every take-off.
A number of factors determine how much runway an airplane needs to take off. These include aircraft weight, thrust, headwind component, and runway conditions. Similar factors affect the amount of runway required to stop, with braking force replacing thrust. The faster an airplane is going, the more dangerous it is to try and stop it, but it's also very dangerous to continue full power off the end of a runway that is not long enough for take-off. It's not the sort of thing you want to be trying to figure out at 250 km/h right after one of your engines has made a very loud noise. The calculations are done using tables, graphs or a computer, and the result is V1, the speed at which the runway required to stop is equal to the runway required to continue. During the take=off run, the non-flying pilot calls out "vee-one" when that speed is reached, and typically the flying pilot takes her hand off the throttles to emphasize that the airplane is committed to flight.
Vee-one isn't necessarily the highest speed at which it is still possible to stop on the runway, but above V1 it's safer to keep going. So V1 is the highest speed at which it is safer to stop than continue, and pilots are supposed to continue if an engine failure is recognized after the vee-one call.
None of this takes into account the possibility that something beyond an engine failure has happened. If the airplane is on fire, or the tail has fallen off, it's clearly better to attempt to stop on the runway, and continue to whatever is beyond the end of the runway, than it is to take a non-airworthy plane into the sky. Here's an account of a captain who decided to abort after V1. They had experienced an engine failure, but the captain believed it to be a bomb, and aborted the take-off, overrunning the pavement. I'm not sure if this particular report mentions it, but I remember one report about this accident mentioned that the captain had once witnessed a takeoff by an airplane that had been damaged too much to fly and had broken up during the go-around. He vowed he would never do that.
There's quite a bit more to say about this, but I'm going to leave it for another entry, because I expect some interesting comments that I'll want to respond to or expand on.