Flight #LH501 from Rio to Frankfurt made a U-turn and is flying back after 2h

This story makes me realize something -- online commercial flight trackers provide a way to detect a flight diversion as soon as radar detects it and possibly before ATC realizes it.

All one would need is an algorithm that uses online resources to track all ongoing flights from any point A to point B. If a flight diverts more than a reasonable amount from a great circle route from one point to another, that should trigger an alarm and extra watchfulness, even though such things sometimes happen for ordinary reasons like a passenger falling ill or an aircraft malfunction.

It's another example of the untapped possibilities of Big Data.