Fog causes flight disruptions at Orly airport

A thick fog at Orly airport led to the stranding of thousands of passengers, primarily due to a failure in the airport's weather data system. The fog, which followed a weekend power outage, caused the diversion of twelve flights and the closure of the airport's apron for over an hour.

Outdated software at the heart of the problem

The core issue was a computer system still running on Windows 3.1, an operating system from 1992. This system was used by the DECOR software, which had been in operation since 1992 at Orly and Roissy airports. Only three technicians in France were trained to maintain this obsolete system in case of failure.

DECOR software's role and limitations

The DECOR software, an acronym for "environmental data control for Orly and Roissy," was responsible for transmitting real-time weather information to pilots and air traffic controllers. It was directly connected to Météo France but operated on software dating back to 1992, running under an operating system that had no official support since December 31, 2001.

System failure and delayed response

According to Le Canard enchaîné, the failure of the system was first reported by Airports de Paris on Twitter, using a reserved formulation that described the issue as a failure affecting "weather tools." The incident occurred on a Saturday morning, when fog caused traffic to stop abruptly, both departures and arrivals. The software had failed as early as Friday evening, but the traffic continued normally until the fog made the failure critical.

Calls for modernization and ongoing delays

Air France confirmed that a computer failure affected the control tower providing weather data. The Ministry of Transport had previously stated that modernization of the equipment was planned for 2017. However, a 2018 Senate report had already pointed out a twenty-year technological delay in French air traffic control compared to its European counterparts, describing the systems of the DSNA towers and approaches as obsolete and disparate.