Why it matters: For the second time in 2023, a minor problem in one location created a ripple effect that grounded many flights over a wide area. Such incidents highlight previously overlooked vulnerabilities in centralized flight control IT systems.

An incident in Frankfurt forced Deutsche Lufthansa AG to ground hundreds of flights worldwide this week. The company said things are returning to normal, but it's alarming that damage in one location could halt air travel globally.

The problem arose when drilling work in northern Frankfurt damaged four broadband cables near Lufthansa's global flight operations center on the outskirts of Frankfurt Airport. Connection problems there started a cascading effect reaching Lufthansa's ground control IT systems globally.

As a result, the company grounded hundreds of flights worldwide, and planes stuck in Frankfurt forced Lufthansa to redirect flights landing there. The company's stock also declined slightly, but not nearly enough to seriously impact its positive performance so far this year.

Deutsche Telekom AG said it wasn't behind the drilling work but has repaired two cables. It can't yet confirm how long it will take to fix the other two but says the work will be tough due to the depth and the extent of the damage. The group seemed surprised that drilling work could reach the cables buried five meters (around 16 feet) underground. Lufthansa said impacted operations like flight check-ins should be restored this week.

However, the company is expected to cancel hundreds more flights starting on Friday due to planned strikes. Lufthansa staff in Frankfurt and Munich are staging a one-day walkout on Friday to speed negotiations over pay and other conditions. The cancellations will likely complicate matters for defense and foreign policy figures attending the 2023 Munich Security Conference.

Lufthansa's IT problems partially mirror what happened in the United States a month ago. Contract workers performing routine maintenance on the Federal Aviation Administration's (FAA) Notice to Air Mission Systems (NOTAM) accidentally deleted critical files, bringing the entire system offline.

Because NOTAM delivers critical information to pilots across the country, this forced the FAA to ground all domestic departures nationwide - over 11,000 - for the first time since September 11, 2001. The January incident drew fire from 120 congressional representatives and triggered congressional hearings.