Four subsea cable faults cut about 30% of Vietnam's international internet capacity

What broke, and when

SJC2 and AAE-1 failed almost simultaneously on 25 August 2026, Telecom Review Asia and SubTel Forum reported [2][3]. SJC2 went down on the S4 segment near Chung Hom Kok in Hong Kong [1][6][7]. AAE-1 lost connectivity on its S1.H2 segment, off Thailand's southern coastline, DTiNews reported [6][7]. That was the first major disruption on SJC2 since the cable entered service in July 2025 [6]. AAG was already under repair from an earlier fault, and IA became the fourth impaired system [2][3].

For users, the practical effect is slower speeds and higher latency at peak times, mainly when reaching overseas social media, streaming services and online games [2][3][8].

Services and websites hosted inside Vietnam should see little impact, because local traffic does not depend on international links [2][3][8]. Operators have not disclosed what caused any of the four faults [2][3][8]. Submarine cable failures most often come from ships dropping or dragging anchors, DTiNews reported, though power problems, maintenance work and technical faults inside the systems also feature [6].

Why 30% is the number that matters

Four of Vietnam's international subsea systems were impaired at once. The country lost roughly 30% of its international internet capacity, a figure several outlets reported within days of the incident [1][3][4][7][8]. VNPT said it began balancing and redirecting traffic through its remaining connections as soon as the faults appeared [3][7]. A representative for the company called it "a force majeure incident that affects all Internet service providers in Vietnam" [7]. A Viettel representative said the SJC2 and AAE-1 failures affected around 30% of the company's own international internet traffic [7].

The operator said service quality was unaffected because it keeps a high level of backup capacity [7]. CMC Telecom said it had anticipated such disruptions and saw little impact on its operations [7].

The stopgap: extra gigabits and a route through Laos

Viettel added 800 Gbit/s of international connectivity through the IA cable and 300 Gbit/s through the Asia-Pacific Gateway, VN Express reported [1][3][8]. Light Reading said further capacity on APG was expected to be added on Monday, 31 August [8]. The operator also rerouted some international traffic over a terrestrial route from Vietnam through Laos to Singapore [3][8]. It planned to raise that route's capacity by 1.5 Tbit/s, and said it could push capacity on its Asia Direct Cable to as much as 50 Tbit/s if needed [3][8].

Those additions are small next to the systems they cover. VietnamNet reported that SJC2 is designed for up to 126 Tbps, of which VNPT owns 9 Tbps [7]. AAE-1 has about 40 Tbps of design capacity, of which Viettel holds 2.5 Tbps [7].

SJC2 cost US$439 million and spans roughly 10,500 km, with a landing point in Quy Nhon [4][6]. AAE-1 is valued at US$820 million, has 19 international partners and runs about 23,000 km from Asia to Europe [6]. Viettel has invested a total of US$50 million in AAE-1 and is the sole partner operating its Vietnamese landing station [7].

Repairs, and a record of repeat failures

Repairs on IA were expected to begin in early September 2026 [2][3]. Reports diverge on AAE-1. Tuoi Tre News said repair work was expected to start in late September, depending on specialized vessels and weather at sea [4]. SubTel Forum, Telecom Review Asia and Light Reading said no repair timetable had been released for SJC2, AAE-1 or AAG [2][3][8]. None of the four systems was new to this. In 2024, faults hit the APG, AAE-1 and IA cables [1][3][8]. In February 2023, all five cables then serving Vietnam were down at once [1][6].

Statistics cited by VietnamNet count nearly 40 incidents since 2022 [7]. The previous AAE-1 fault, in late February 2026, cut an estimated 8 to 10% of Vietnam's international capacity, DTiNews reported [6].

The Vietnam Telecommunications Authority put the loss at nearly 10%, or about 45,000 Gbps, and said no localised service interruptions were reported [5]. Even the count of Vietnam's cables is not settled. Data Center Dynamics, Tuoi Tre News and VOV.VN describe six systems in service [1][4][5]. DTiNews lists eight, adding SMW-3 and TVH [6].

What happens next

Vietnam plans to add at least 10 new subsea cable systems by 2030, which would take the total to 15, according to Light Reading and Telecom Review Asia [3][8]. Light Reading reported that the 2024 outages prompted the Ministry of Information and Communications to approve the plan [8]. Land routes are part of the answer too. Vietnam took full control of the Vietnam-Singapore Terrestrial Cable Network in 2025; it is designed for 4 Tbps and scalable to 12 Tbps, VOV.VN reported [5]. Starlink was licensed in mid-February 2026, but its rollout schedule and domestic pricing have not been announced [5].

Neither the causes nor a repair timeline for SJC2, AAE-1 and AAG has been made public. All three remain without a published return date [2][3][8].