"Analysis by the British satellite company Inmarsat and the UK's Air Accidents Investigation Branch (AAIB) was cited on Monday by the Malaysian prime minister as the source of information that has narrowed the location where the Malaysia Airlines flight MH370 may have crashed into the southern Indian Ocean to a corridor a couple of hundred miles wide."
The new method "gives the approximate direction of travel, plus or minus about 100 miles, to a track line", Chris McLaughlin, senior vice-president for external affairs at Inmarsat, told Sky News"
For AF 447, BEA used the sat data to narrow the search area when it was found by Swire Seabed...it was found long after the pingers stopped working.