Dozens of United Airlines flight has been delayed worldwide after  a “systems issue” has cropped up.

A spokesman for United told the media that, they are aware of an issue with their systems that is resulting in flight delays. They are working to resolve the issue and get the customers to their destination as soon as possible. They have apologized for the inconvenience caused.

More than 60 flights are known to have been delayed. The first flight from the UK was due out from Heathrow at 7.30am, to Washington DC, but left an hour late. Passengers were told it was “delayed due to operational difficulties”.

United is the world’s third-biggest airline, after Delta and American.

United Airlines later announced on its Twitter that the issue was resolved at 8.15am UK time, and all flights have resumed.

In August, Delta Airlines – the world’s biggest carrier – experienced a worldwide systems failure which led to the cancellation of hundreds of flights and delays to thousands more. The airline blamed a power problem, and denied that its system had been breached, but cyber-security experts were skeptical.

Passengers expressed their frustration for the delay through various social media platforms.