How long a runway?
Assuming the pilots of Malaysia Airlines Flight 370 didn't destroy the plane; assuming they didn't crash-land it either; and assuming instead they got it to an airfield, how long would the runway have to be to accommodate a jet as large as a Boeing 777?
According to the plane's manufacturers, anywhere between 1200 and 2500 metres. The variable factors are: the altitude of the runway (the higher it is, the longer it has to be); the weight of the plane; and the weather. A 777 at its maximum landing weight arriving in the rain at high altitude requires twice the distance to land as an unladen 777 landing at sea level on a dry runway.
Vast as the search area for MH370 may be, there aren't thousands of airfields with runways at least 1100 meters long. So you'd think the places to look could be narrowed down.
And yet. Boeing 777s have such excellent crash-landing records. It is the safest commercial airliner ever built. The British Airways flight from Beijing to Heathrow that crash-landed in 2008 came to a halt in no distance at all. The plane touched down before reaching the tarmac, the undercarriage and one of the engines were ripped away, fuel leaked from the plane but didn't ignite. The co-pilot, John Coward, who brought the plane down safely, was said to be a hero.
In other words, if MH370 didn't disappear into the ocean, and was landed by whoever was in control of it, then the area to search remains absolutely vast. Several hundred metres of flat grassland might be all that was needed to bring it to a stop.