An IT system outage at French air navigation service provider DSNA on Sept. 1 caused major delays at airports in France and neighboring countries.

The computer crash caused delays of 30 min. to an hour-and-a-half at French airports.

The failure, deemed “exceptional” by French civil aviation authority DGAC, added to problems in a region where flight punctuality is a challenge.

The outage started Sept. 1 at 2:30 a.m. local time. It affected the DSNA’s aeronautical message switch system, which exchanges flight plan and takeoff slot data between Eurocontrol’s and DSNA’s initial flight plan processing systems (IFPS), DSNA director of operations Eric Bruneau said.

The first backup scheme did not work and DSNA resorted to a spare arrangement. By 9:00 a.m., it was operational, and by 11:30 a.m. the IFPS database was rebuilt, according to Bruneau.

In the meantime, however, air traffic controllers had to manually enter flight plans. The extra workload meant that each controller could take care of fewer aircraft than usual. At the worst time in the morning, ATC capacity was down by 30%-50%, Bruneau said.

Not every airport felt the full impact of the outage, as the capacity reduction did not necessarily happen at peak times, depending on the airport.

At 11:30 a.m., DSNA’s management team chose not to lift capacity limitations simultaneously at all five en-route control centers. Such a situation could have suddenly sent too many flights into French air space, threatening safety, Bruneau explained. Therefore, the capacity ramp-up was gradual and the average delay was reduced progressively in the afternoon.

Using an extra runway at Paris’s Orly Airport helped. Usually, two runways are in service, 06-24 and 08-26. But the latter is undergoing renovation work and is closed until late next month.

A third runway, 02-20, was scheduled to provide some takeoff capacity from Sept. 2, but given the abnormal circumstances, was placed in service Sept. 1 for 14 takeoffs in the 4:20-5:10 p.m. time slot.

The third runway is usually not in service because of its noise footprint, but Bruneau said the mayors of the surrounding towns were informed about the change of plan.

An investigation into the outage has begun and air navigation service providers in Switzerland and Germany, as well as Eurocontrol, are included, he said.

DSNA said it may devise a more flexible spare system if another outage should occur. It could be activated at subsystem level, rather than the entire system, Bruneau suggested.

DSNA’s systems are relatively old and a multi-year upgrade plan is ongoing, according to the SNCTA controller union. DSNA’s annual investment in IT tools stands at €300 million ($330 million), according to national secretary Loic Parisi.

Because of a downturn in the air transport industry in the early 2010s, the annual budget was much lower, at around €150 million, he said. But traffic has since grown faster than expected, making the investment insufficient. Some routes in France are experiencing a 15% annual expansion and some airports report an 8%-10% annual growth, he said.

Thierry Dubois, thierry.dubois@aviationweek.com