Analysis of flight recorder data from the deadly Air India crash two weeks ago was underway in India after investigators successfully retrieved the information from the two black boxes on board.

India would not allow a UN investigator to join a probe of a crashed Air India jet that some safety experts had criticized for delays in analysis of crucial black box data, two senior sources familiar with the matter told Reuters.

The data from the recorders can be used to reconstruct the flight's final moments and determine the cause of the incident.