Air India plane crash: What is a black box, how it works

This handout taken and posted on the X (formerly Twitter) account of the Central Industrial Security Force (CISF) On June 12, 2025 shows the back of an Air India plane after it crashed in a residential area near the airport in Ahmedabad.

While speculation is rife about what caused the London-bound Air India plane carrying 242 passengers to crash into a residential area in Ahmedabad minutes after taking off from the Sardar Vallabhbhai Patel International Airport on Thursday afternoon, all eyes are on the aircraft's black box to understand what caused the tragedy.

According to Air India, the flight had 169 Indians, 53 British, and one Canadian national on-board.

Rescue teams are continuing their search for survivors while investigators are working on recovering the black box situated at the tail-end of the aircraft.

Here is how a black box helps investigators find out more about a plane accident:

The “black box” is usually two different boxes with different functions. The name itself is a misnomer because neither of these are black nor resemble a box.

What is it made of?
The black box is made of two separate pieces of equipment: Flight Data Recorder (FDR) and Cockpit Voice Recorder (CVR).

What is its colour?

Contrary to its name, black boxes are not black. They are bright yellow or orange. The bright colour is used to assist in locating the boxes after an accident. Before airlines made day-glow orange a standard colour for the flight recorders, some Boeings used a yellow sphere.

Why is it called so?

There are several theories about the origin of the name “black box”. The most widely accepted one refers to the early black box designs which were dark inside. Another view is that it got its name from its charred look due to post-accident fires.

What does it look like?

Black boxes don’t look like boxes. The device may come in a variety of shapes, including spheres, cylinders and domes. It has to be large enough for investigators to find among the plane’s debris.

How is it traced after plane accidents?

Black boxes have an underwater locator beacon that starts emitting a pulse if its sensor touches water. They can only be detected if the aircraft is under water. If a crash happens on land, investigators have to depend on its orange colour that acts as a beacon.

What does FDR do?

The flight data recorder (FDR) records more than 80 different types of information such as speed, altitude and direction, as well as pilot actions and performance of important systems. The FDR records aircraft system and flight data, such as the position of control surfaces (flaps, elevator, rudder, ailerons), barometric data (altitude, airspeed, vertical speed, engine performance, etc)

What does CVR do?

The Cockpit Voice Recorder (CVR) records radio transmissions and other sounds in the cockpit, such as conversations between the pilots, and engine noises. The CVR is a multi-track audio recorder that continuously captures every audible sound in the cockpit.