Today, Friday, a search vessel recovered the Flight Data Recorder, the second of the two black boxes from EgyptAir 804.  The Flight Data Recorder maintains a continuous log of the last 25 hours of aircraft technical data, including engine information, hydraulic and electrical systems.  If there was a mechanical issue with the aircraft, this Data Recorder should be able to point investigators towards the malfunction or series of failures that brought the A320 down nearly a month ago.

SV John Lethbridge debris 2
Photo credit SV John Lethbridge