The flight data recorder and cockpit voice recorder, or black boxes as they are often called, store data about planes.
They can provide vital information in air accident investigations.
The flight data recorder from the Ethiopian Airlines plane which crashed on Sunday, arrived in France on Thursday morning for inspection by the Bureau of Enquiry and Analysis for Civil Aviation Safety (BEA), the French version of the UK’s Air Accident Investigation Branch.
BBC Africa’s takes a look at what’s inside a flight data recorder.
Video journalist: George Wafula.