SEOUL — North Korea's trash balloon campaign, missile launches and the emergence of GPS "spoofing" have increased risks in South Korean airspace, aviation experts say, complicating airline operations as tensions rise between the rival nations.
In late May, North Korea began floating thousands of balloons carrying bags of trash, including human excrement, into South Korea, in what analysts say is a form of psychological warfare.
Hundreds of balloons landed in the South during seven waves between May 29 and June 27, including one on a runway at Incheon airport, forcing a three-hour suspension of take-offs and landings at its biggest international gateway.
When the balloons first appeared, aviation navigation interference from North Korea also spiked, including what appears to be the first bout of so-called "spoofing" affecting commercial aircraft in the South.
"Airspace safety is gradually deteriorating," OPSGROUP, a membership-based organisation that shares flight risk information, said in a June bulletin. "There are no official airspace warnings for South Korea, but the risk situation seems to be getting worse."
South Korea's Transport Ministry said its military, air traffic control authorities and airlines maintain a 24-hour surveillance and communication system.
"The South Korean military detects these balloons using surveillance assets… day and night," a military spokesman said, without giving further details.
North Korea, which also launched trash balloons in 2016, says they were retaliation for propaganda campaigns by North Korean defectors and activists in the South who send items via balloon.
The balloon flights have several times shut down operations at Incheon, the world's fifth-busiest international airport and an important cargo hub, about 40km from North Korea.
The balloons have made flying in the area "quite complicated", said Yun Chan-hwang, general manager of network operations for Korean Air Lines, which has adapted procedures to deal with the new hazard.
If northerly winds are expected, the airline adds fuel to flight plans so aircraft can stay aloft longer or divert to alternative airports, Yun said.
Disruption caused by the balloon campaign is being exacerbated by increased signs of interference to the global positioning system (GPS), a network of satellites and receivers used for navigation.
Militaries and other actors can broadcast signals that trick a GPS system into thinking it is somewhere it is not.
"This could lead pilots to drift off course, with the risk of straying into North Korean airspace," said Kari Bingen, the aerospace security project director at the Washington-based Centre for Strategic and International Studies.
Between May 29 and June 2, about 500 planes and hundreds of ships experienced GPS problems, South Korea's government said. It complained to the UN's International Civil Aviation Organisation (ICAO), which warned North Korea to stop.
GPS interruptions in the South from North Korea have occurred for more than a decade, but spoofing appears new, said SkAI, a Swiss company that runs a live disruption map.
SkAI detected spoofing in South Korean airspace between May 29 and June 2 that affected dozens of planes, the company's co-founder Benoit Figuet said.
"Some of the impacted aeroplanes were flying quite low in altitude. We even have seen aeroplanes being spoofed while being on the ground," Figuet said.
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Notifications to pilots issued by South Korea in May and June warned planes flying around Incheon and Seoul to "exercise extreme caution when using GPS".
No major aviation accident has been linked to GPS spoofing globally, but a business jet flying from Europe to Dubai nearly entered Iranian airspace without clearance in September 2023, OPSGROUP said.
North Korea said in 2023 it would shoot down anything it deemed a reconnaissance flight entering its airspace.
Most airlines avoid North Korean airspace. The US Federal Aviation Administration bans overflights of North Korea for reasons including unannounced ballistic missile tests, air defence capabilities and potential electronic warfare.
"South Korea's airspace is at constant risk of instability caused by some kind of political crisis," OPSGROUP said. "Things have potential to change quickly, and without warning."
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