Japanese telecommunications company KDDI Corporation suffered the worst outage ever, taking nearly 40 million customers offline on Saturday morning. The outage began around 01:35 Although internet and communication services have been largely restored, mobile phones are still struggling to make phone calls due to the temporary restriction of network traffic. Of the 40 million customers affected, approximately 260,000 belonged to the corporate sectors. The deduction has corrupted payment machines, bank tellers, package delivery, and even weather information from the weather agency.

KDDI is the second largest mobile operator in Japan. The company says the problem was caused by a malfunction at the facility before dawn on Saturday. The malfunction was caused by a voice call replacement system that was replaced during scheduled maintenance. The repair works caused traffic congestion, which forced the company to impose restrictions.

At a press conference, Cabinet Deputy Secretary General Seiji Kihara said that the problem is extremely unfortunate, as mobile networks are an important infrastructure for the population and their activities. It also requested “in-depth explanations for users” from the operator.

KDDI President Makoto Takahashi apologized for the glitch at a press conference and acknowledged that it was the biggest glitch in the company’s history. The carrier is also considering compensation for individual and corporate users. The carrier takes measures such as flow control to reduce congestion for voice calls and data.

Especially the ATMs in Ogaki Kyoritsu Bank are not working as of Monday morning. Yamoto Transport Co said the delivery system was broken. Drivers using Toyota’s connected car service were unable to contact the call center or perform other tasks. The issue has also affected low-cost mobile brand UQ and mobile customer “povo” and other smaller rental companies such as Rakuten Mobile Inc. KDDI advised people to use landlines or payphones in emergencies. Source