RTX's Muse Ransomware Knocks Airports Back to Paper - Brussels Cancels Nearly 50% of Flights, Airline Shares Slip up to 1.3%

Ransomware that hit the check-in software used at several big European airports knocked travel back to the paper era for a while - and the market noticed.

The problem traced to Collins Aerospace's Muse check‑in and boarding platform, part of RTX Corporation (NYSE: RTX). Airports including Heathrow, Brussels, Berlin and Dublin switched to manual processing after the outage began on Friday, creating long queues, cascading delays and a string of cancellations. Brussels Airport said it scrapped almost half its scheduled departures on Monday while technical and security issues remained unresolved.

The European Union Agency for Cybersecurity (ENISA) confirmed a third‑party ransomware intrusion was behind the disruption, and law enforcement units have opened an investigation.

Short‑term market reaction was clear: European carrier shares drifted lower in morning trade. Deutsche Lufthansa AG (XETRA: LHA), International Consolidated Airlines Group (LSE: IAG), Air France‑KLM (Euronext: AF), easyJet (LSE: ESYJY), Wizz Air (LSE: WIZZ), Ryanair (OTC: RYAAY) and TUI (LSE: TUI) were all trading down, roughly in the 0.5%-1.3% range as of 04:53 ET (08:53 GMT).

Airports said online and self‑service check‑ins continued to work, but the switch to manual counters and paper manifests slowed throughput significantly. The knock‑on effect was flight delays and cancellations that fed back into weaker sentiment for carrier stocks during early trading.

For traders watching the sector, the incident flagged a non‑aviation risk that can hit operations hard: third‑party software vulnerabilities. Where airline revenue and schedules are scaffolded on shared IT platforms, one outage can ripple across several carriers at once.

No ransom payment details or claims of responsibility have been released publicly yet. Authorities and the affected vendors are working to restore systems and to determine how the attackers gained access.

Passengers were urged to check flight status pages and to use online options where possible while airports recovered. The markets, for now, priced the story as a short‑term shock - but the episode is a reminder that cybersecurity failures can translate into tangible operational disruption and immediate share‑price reactions.

How long the damage to sentiment lasts is anyone's guess - but Monday's trading gave a quick read on how sensitive airline equities are to operational headlines.