By Greg Torode
HONG KONG, Feb 26 (Reuters) - A large Chinese military drone has conducted regular flights over the South China Sea in recent months while transmitting false transponder signals that made it appear to be other aircraft, including a sanctioned Belarusian cargo plane and a British Typhoon fighter jet.
Military attaches and security analysts scrutinising the operations say the flights represent a step-change in China's grey-zone tactics in the contested South China Sea and appear to be testing possible decoy capabilities in the event of a Chinese invasion of Taiwan.
Since August, at least 23 flights have been logged under the call sign YILO4200, a known long-endurance Chinese military drone, but the aircraft transmitted registration numbers of other aircraft, according to Reuters analysis of data from flight-tracking website Flightradar24.
The flight paths often head east from the Chinese province of Hainan towards the Philippines, near the disputed Paracel Islands, and down Vietnam's coast, the flight analysis showed.
Reuters is reporting the scale and complexity of the operations for the first time.
The operations represent a new and elaborate element in China's expanding presence across the South China Sea and around Taiwan as its military responds to Communist Party demands to sharpen the readiness of its forces, according to three regional diplomats, four open-source intelligence analysts and three security scholars familiar with the flight data. The activities include exploiting electronic warfare and deception tactics in real time, they said.
And while the masking is unlikely to fully deceive air traffic controllers or military-grade radars, it could sow time-wasting confusion in a conflict, conceal sensitive surveillance activity or be used for propaganda or misinformation, the envoys and intelligence analysts said.
"We've not seen anything like this before," said Ben Lewis, founder of the open-source data platform PLATracker.
"It's ... a kind of deception trial being carried out in real time using aircraft that are not exactly low profile. It does not appear to be at all accidental."
China's defence ministry didn't respond to Reuters questions about the flights and their purpose.
BELARUSIAN CARGO PLANE
The flights have mostly appeared on Flightradar24 as an Ilyushin-62 cargo plane operated by Rada Airlines of Belarus but also a Royal Air Force Typhoon, a North Korean Il-62 passenger jet and an anonymous Gulfstream executive jet.
Since mid-December, YILO4200 has also made several flights in northwest China, most recently on February 15 when it appeared as an anonymous Pilatus PC-12, a small turboprop passenger aircraft.
Aircraft registration numbers stem from a coded so-called 24-bit address governed by the International Civil Aviation Authority. Broadcast via transponders, the numbers help reveal an aircraft's position, direction and speed.
While unique to each aircraft, the addresses are publicly known and two pilots and two analysts say recoding a transponder to give it a different registration number is possible.
Rada was sanctioned by the U.S. Office of Foreign Assets Control in August 2024 for flying cargoes in and out of Africa that included Wagner Group personnel linked to the Russian military, as well as exotic wildlife trafficking.
The real Belarusian Il-62 has been active throughout the period with a different call sign and was once airborne at the same time as the Chinese drone attempting to mask it, the Flightradar24 data showed.
Rada Airlines did not respond to a request for comment and Britain's defence ministry said it could not comment.
An ICAO spokesperson said the body does not comment on issues or speculation concerning specific member states.
OPERATION COULD SOW CONFUSION
Flying out of Hainan's Qionghai Boao International Airport, the aircraft frequently remained airborne for hours, flying star- or hourglass-shaped patterns over the same areas.
The flight profiles matched those typically associated with large military drones on surveillance operations and covered sensitive parts of the South China Sea, including areas frequented by submarines, four intelligence analysts familiar with the data said.
The Chinese military generally flies its drones "dark", transmitting neither call signs nor registration numbers.
Two flights among the 23 reviewed by Reuters appeared to be particularly unusual: In one, that straddled August 5 and 6, the drone initially transmitted a code belonging to the RAF Typhoon, then switched signal to three other planes over about 20 minutes, eventually landing as the Rada Airlines plane.
In another, on November 18, the drone was airborne purporting to be the Belarusian plane when the actual Rada Il-62 plane took off near Belarus headed for Tehran.
Singapore-based security analyst Alexander Neill said the Hainan operations appeared to be a fresh tactic in a suite of Chinese digital options to "muddy the waters" should regional tensions escalate into conflict.
"They don't appear to be exercises as much as the kind of action the U.S. Indo-Pacific Command has described as rehearsals for a confrontation - anything the Chinese can do to sow confusion in the minds of their rivals is to their advantage," said Neill, a fellow at Hawaii's Pacific Forum.
"The U.S. and its allies know that given the realities of highly automated conventional conflict, even milliseconds count along the kill chain of escalation."
The Pentagon did not respond to a request for comment on the Chinese drone flights.
Lewis and three other open-source intelligence analysts said the YILO4200 call sign came from long-endurance Wing Loong 2 unmanned aerial vehicle, an aircraft similar to the U.S. Reaper drone, with a wingspan of 20.5 metres (67 feet).
The Wing Loong is used mainly for surveillance but can be fitted for other tasks, including command and control operations, precision missile strikes and anti-submarine operations.
It is produced by the state-linked Chengdu Aircraft Corporation, a subsidiary of AVIC. The company said it would not be commenting on the issue.
Online flight tracker Amelia Smith first connected the Wing Loong 2 to the call sign by analysing flight data, state press reports and government announcements.
Lewis, Smith and two other intelligence analysts said it was unclear which Chinese agency was operating the aircraft out of Boao Airport, which is a dual-use commercial and military facility.
Satellite images from July, September and January obtained by Reuters show large drones on the tarmac, alongside support buildings in a part of the airport now being expanded.
REHEARSAL FOR TAIWAN
Flightradar24 communications director Ian Petchenik said the tracker had noticed the Hainan flights and had not seen such activity before, beyond apparently accidental miscodings, non-existent addresses or corrupted data.
"Based on the flight patterns and the kind of usage of these 24-bit addresses, it doesn't seem like it is a mistake in the programming of the transponders," Petchenik said.
Reuters couldn't determine whether the flights are running on programmed paths or being controlled from the ground.
The paths run through areas of heavy naval activity, including the waters south of Hainan near Chinese submarine bases and east toward the Bashi Channel between Taiwan and the Philippines - a key choke point for China's navy to access the Pacific.
The route patterns suggest a rehearsal for an operation over Taiwan, said Neill, the security analyst.
Overlaid on a map of Taiwan, the 23 flight paths pass multiple military points of interest, concentrated around Taipei but also extending along the island's southern coastline. The eastern trajectories bring the aircraft close to Japanese and U.S. bases in Okinawa and other islands in the Ryukyu chain.
"It is a compelling image - extensive rehearsals across the South China Sea to be deployed over Taiwan's key points," Neill said.
(Reporting By Greg Torode in Hong Kong; Additional reporting by Karen Lema in Manila, Idrees Ali in Washington, Gleb Stolyarov in Moscow, Sam Tabahriti in London and Beijing newsroom; Editing by Joe Brock and Lincoln Feast.)
