SQ321 weather radar gave no warning before fatal turbulence, TSIB final report finds

Singapore's Transport Safety Investigation Bureau (TSIB) has released its final report into Singapore Airlines (SIA) Flight SQ321, finding that the aircraft's on-board weather radar gave no warning before severe turbulence killed one passenger and injured 79 others.

The report was published on Monday, 19 May 2026 — two days before the second anniversary of the incident.

The Boeing 777-300ER, carrying 211 passengers and 18 crew from London to Singapore, encountered severe turbulence over south-west Myanmar on 21 May 2024 while cruising at 37,000 feet.

The TSIB, a department within Singapore's Ministry of Transport, said it could not conclusively determine whether the weather radar had malfunctioned. While the manufacturer's tests found no evidence of failure, the bureau said the possibility "cannot be ruled out".

The aircraft was flying at a speed of 0.84 Mach, or 1,037 kilometres per hour, when the turbulence struck at about 3.49pm Singapore time.

The digital flight data recorder showed that within 19 seconds, vertical acceleration ranged from plus 0.44G to plus 1.57G.

In less than a second, the acceleration plunged from plus 1.35G to minus 1.5G, sending passengers who were not belted up into the air. The G-force then increased to plus 1.5G over the next four seconds, bringing them down.

Pilots see no clouds

Two captains were in the cockpit at the time — a pilot-in-command and an augmenting pilot — while a senior first officer was resting in the crew rest area.

The augmenting pilot deployed the speed brakes after noticing the aircraft was about to exceed its maximum operating speed.

The pilot-in-command reduced cruising speed to 0.82 Mach — the recommended speed for flying through turbulence — and activated the seat belt sign. There was no time to make a cabin announcement.

The autopilot pitched the aircraft's nose down to maintain the cruising altitude, but the plane continued to climb to 37,362 feet. SIA suggested that the aircraft had likely encountered an updraft — a fast-rising column of air — with a speed of 8,000 to 9,000 feet per minute.

The TSIB found that the pilot-in-command had set the weather radar at its highest sensitivity throughout the flight, a setting that amplifies precipitation detected. Despite this, the navigation displays showed no weather returns.

Cockpit voice recordings captured the pilot-in-command saying after the event: "We hit something, but I was on MAX … I was on MAX, I don't see anything here."

Visual inspection by both pilots also indicated clear skies in the immediate flight path, with only high-level clouds visible in the distance.

Other aircraft observed widespread clouds

The TSIB noted that three other aircraft flying in the area at the time were in clear visual conditions and observed widespread clouds, deviating from their planned routes to avoid the weather.

Their flight crews estimated cloud-top heights of between 35,000 and 50,000 feet. These aircraft used different weather radars from the one on SQ321.

"The investigation team is unable to understand why the flight crew of the occurrence flight did not see the widespread clouds," the bureau said.

The TSIB added that the actions of the flight crew were "understandable and appropriate for the situation" in the face of the unexpected event.

History of radar issues

The TSIB cited maintenance records showing that the same aircraft's radar had failed to display weather events as recently as six days before the turbulence incident.

On 15 May 2024, the radar failed to display any information despite the flight crew observing storm clouds outside the cockpit. Earlier malfunctions on the right-hand side radar were recorded on 29 April 2024 and 1 May 2024.

Pilots ferrying the turbulence-stricken plane from Bangkok back to Singapore on 26 May 2024 also noted that one of the two weather radars was displaying less information compared with the other.

Data from SIA showed that out of 29,000 flights involving its Boeing 777 fleet between May 2023 and July 2025, 103 flights experienced weather radar issues. Three of these involved the aircraft used for Flight SQ321.

Because no error messages are generated during such malfunctions, the TSIB advised flight crew to closely compare external visual cues with what is displayed on their screens.

TSIB recommendations

The bureau made several safety recommendations.

It called on the International Civil Aviation Organization (ICAO) to mandate a recording function on all aircraft with a maximum take-off mass exceeding 27,000 kilograms that were officially certified before 1 January 2023.

Currently, only aircraft certified after that date are required to have the function, which would have allowed investigators to view what the flight crew saw on their navigation displays. The aircraft operating Flight SQ321 entered service in 2008.

The TSIB also recommended that Boeing guide flight and maintenance crew on how to ascertain whether a weather radar is malfunctioning, and that the radar manufacturer develop a way to record images of weather information displayed to crew.

Emergency landing in Bangkok

After the turbulence subsided, the flight crew declared a Mayday at 8.01am UTC and requested a diversion to Bangkok.

The aircraft landed at Suvarnabhumi Airport at 8.45am UTC, where medical personnel were waiting to treat the injured.

SIA has since improved its turbulence monitoring and awareness tools, issued guidance to crew on troubleshooting suspected weather radar malfunctions, and committed to sending reports of such issues to Boeing and the radar manufacturer for follow-up.