MH370 Vanished From the Systems Watching It

On March 8, 2014, Malaysia Airlines Flight MH370 disappeared while flying from Kuala Lumpur to Beijing with 239 people aboard.

Air traffic controllers lost contact with the Boeing 777, and its identifying signal vanished from their radar screens. Military radar continued tracking an aircraft for a time, but eventually that contact disappeared too.

Yet something aboard MH370 was still communicating. Far above the Indian Ocean, an Inmarsat satellite was receiving automatic responses from equipment inside the missing aircraft.

Nobody was speaking to the pilots, and nobody knew where the plane was going. But for hours after ordinary tracking ended, the satellite system continued receiving signals.

The First System Went Quiet

MH370 departed Kuala Lumpur shortly after midnight local time, carrying 227 passengers and twelve crew members. The aircraft was following its scheduled route toward Vietnam when, at 17:07 UTC, it transmitted a routine message through its ACARS communications system.

Fourteen minutes later, its transponder stopped providing the identifying information civilian controllers depended upon. Without that signal, the aircraft could no longer be tracked in the usual way.

Malaysia’s military radar, however, could still detect a physical object moving through the sky. What it recorded next was alarming.

The Aircraft Had Turned Around

Instead of continuing toward Beijing, radar showed an aircraft turning back across the Malay Peninsula. It traveled westward, crossed toward the Strait of Malacca, and eventually headed northwest, far from MH370’s planned route. Military radar maintained contact until approximately 18:22 UTC.

Investigators would later use those observations to reconstruct the aircraft’s unexpected movements. Just three minutes after the final radar contact, another electronic system suddenly became active.

At 18:25, a Machine Logged Back On

At 18:25:27 UTC, MH370’s satellite data unit initiated a new connection with the Inmarsat communications network. The equipment normally handled satellite communications aboard the aircraft. Its routine exchanges weren’t intended to replace radar or provide a continuous record of the plane’s location.

Investigators concluded that the system had experienced some kind of interruption before reconnecting. The records couldn’t explain what caused it, but the successful log-on showed that the equipment was operating again. More exchanges followed over the next several hours.

The Satellite Kept Asking. MH370 Kept Answering.

Satellite communications equipment periodically exchanges short signals with the network to confirm that a connection is available. These automatic exchanges are sometimes called handshakes. A ground station sends a signal through a satellite, and the aircraft’s equipment responds without requiring anyone in the cockpit to do anything.

At one point, a satellite telephone call was attempted. The system responded, but nobody answered.

Engineers examining the records realized the signals contained clues that hadn’t originally been intended for locating aircraft. They began studying the information hidden in those ordinary exchanges.

Tiny Differences in the Signals Became Clues

One important measurement was the time required for a signal to travel between the aircraft and the satellite network. Because radio signals move at a known speed, that delay helped researchers estimate the aircraft’s distance from the satellite.

Rather than producing a single point on a map, each measurement created an enormous curved line of possible locations across Earth’s surface. Investigators called these lines arcs.

Engineers also studied small changes in the frequency of the signals, which helped them estimate how the aircraft was moving relative to the satellite. Combining the measurements pointed toward a southern flight path into the Indian Ocean.

A passenger jet that had been expected in Beijing appeared to have traveled far out over remote waters instead.

The Last Message Arrived at 00:19

The final recorded satellite exchange began at approximately 00:19 UTC on March 8. It involved another log-on, suggesting the satellite equipment had restarted after an interruption to its power supply.

Investigators considered whether fuel exhaustion and changes in the aircraft’s electrical systems could explain what happened. They also examined the final frequency readings, which were consistent with a high rate of descent near the end of the flight.

Those last measurements helped define the seventh arc, an important reference for later underwater searches. After that exchange, the satellite network heard nothing more.

Pieces Began Washing Ashore

In July 2015, a piece of aircraft wreckage washed ashore on Réunion Island in the western Indian Ocean. It was a flaperon, a movable section of a wing that helps control an aircraft during flight. Investigators confirmed that it came from MH370.

Other pieces were subsequently discovered along coastlines around the western Indian Ocean, offering further information about the aircraft’s fate. But the main wreckage remained missing, along with the flight data recorder and cockpit voice recorder.

Those devices could reveal details about the aircraft’s final operating conditions that the satellite communications couldn’t provide. Finding them required an enormous underwater investigation.

Underwater Robots Joined the Search

The southern Indian Ocean is one of the most difficult places in the world to search. Some areas are thousands of metres deep, with rugged terrain that must be examined using specialized underwater equipment. Ships carrying sophisticated sonar systems have spent years looking for MH370.

In March 2025, Malaysia signed an agreement with marine exploration company Ocean Infinity to search a targeted area of approximately 15,000 square kilometres. The company deployed underwater survey technology capable of mapping large sections of the seabed. By early 2026, roughly half the designated area had been examined without finding the aircraft.

In June 2026, Malaysia extended the agreement through June 30, 2027, allowing work to continue across the remaining area.

The contract was structured so that Ocean Infinity would be paid only if the missing aircraft was found.