From ATSB Fact Sheet
At the time MH370 reached the 7th arc, the aircraft is considered to have been descending. A study completed after the Air France 447 accident concluded that the majority of aircraft in loss of control accidents were found within 20 nautical miles (32 km) of their last known position. This provides a reasonable limitation for the size of the search area across the arc.
The above differs somewhat from the findings of MAK/IAC, i.e.
- The distance of the impact point from the initial point of upset depends mostly on the type of upset and, sometimes (in dives and unclosed spirals), from the duration of coming down. In spins and closed spirals the impact point location has significantly lower correlation with the duration of coming down. In any case the distance is hardly possible to be more than 12 NM.
- The average time interval of loss of 1 km of altitude is shortest for dives and longest for spins, but in any case it seems hardly possible to be more than 14-16 seconds. It means that for AF447 flight, with cruise altitude of about 10700 meters, the duration of coming down was less than 3 minutes.