A cyberattack targeting Collins Aerospace’s MUSE (Multi-User System Environment) caused major disruptions to check-in and boarding systems across Europe. There were chaotic scenes at airports across the UK, Germany, Belgium, Ireland, and other countries as travelers were left unable to check in, and hundreds of flights were canceled.

The outage began on Friday and has persisted into multiple days. According to an internal crisis communications document obtained by the BBC, over a thousand computers were affected at London’s Heathrow airport alone. Check-in and boarding staff were also instructed to use manual workarounds throughout the recovery process.

It also revealed that the threat actors were able to persist inside airport systems even after Collins rebuilt and relaunched its systems in an attempt to eject them. In some cases, the corruption was so severe that not even remote restoration was feasible. The European Union Agency for Cybersecurity (ENISA) says a ransomware attack was the cause.

The impact remained significant up until Tuesday, 23 September. Data from FlightRadar shows that 80%+ of flights were delayed at major airports like Heathrow, Gatwick, Schiphol, Madrid, and Rome (FCO). Brussels Airport was also forced to cancel 140 flights on Monday. Airports were expecting continued minor disruptions throughout Wednesday or Thursday as well, but delays had dropped to the 30-40% range at the time of writing.

The UK’s NCSC said that it was “working with Collins Aerospace and affected UK airports, alongside the Department for Transport and law enforcement colleagues, to fully understand the impact of the incident.”

No threat actor has claimed responsibility for the incident as of yet. However, researchers suspect ShinyHunters or its partner Scattered Spider is to blame. Both gangs are notorious, with ShinyHunters being implicated in an ongoing wave of Salesforce data breaches. Earlier this year, Scattered Spider also aggressively targeted US companies with sophisticated social engineering and ransomware attacks.

Collins Aerospace is one of the world’s largest aerospace and defense solutions companies, owned by RTX (formerly Raytheon). Airports around the world use its software for check-in and boarding procedures, including managing luggage as well as printing boarding passes and luggage tags.