Airlines worldwide were forced to delay flights Thursday as a global flight-bookings system operated by Amadeus IT Group SA suffered what the company called a "network issue."

Carriers including British Airways, Deutsche Lufthansa AG, Cathay Pacific Airways Ltd. and Qantas Airways Ltd. were among those impacted, with Dutch operator KLM delaying at least 24 departures. Singapore's Changi airport said via Twitter that a technical problem affecting some operators was holding up the check-in process, with boarding passes having to be issued manually.

"Amadeus confirms that, during the morning, we experienced a network issue that caused disruption to some of our systems," the Madrid-based company said in a statement. Some airlines reported that they were affected by the glitch for a matter of minutes, though it was 3 1/2 hours before Amadeus was able to say that the network was "functioning normally."