A widespread computer outage temporarily grounding Southwest Airlines flights has been blamed on the 'IT backbone' which supports several major airlines worldwide.

According to outage-tracking website Downdetector, the major carrier experienced an issue with their system preventing them from checking in flyers or customers using the airline's app.

Passengers in multiple cities claimed on social media that they were stuck at airport terminals, unable to board or take off due to the outage.

One flyer in Denver claimed Friday morning: 'Southwest Gate staff announcing system wide outage and all planes not in the air are stopped across the country.'

Temporary systems outages were reported in California, Florida, Maryland, Ohio, Tennessee and Utah Friday morning. Some Southwest passengers were also reportedly unable to pay for their baggage online amid the system outage.

The issues began just after 8am ET, with some flyers posting they were 'sitting in the terminal waiting on their computer system to hopefully come back to life.' 

An airline spokesperson told the Daily Mail: 'Southwest experienced a brief interruption due to a system outage at our vendor, Amadeus. The airline continued to check baggage and board flights manually while full functionality was restored.'

'We apologize to our Customers for any inconvenience and hope to get them to their destinations as quickly as possible. Nothing is more important to Southwest than the Safety of our Customers and Employees,' the spokesperson added.

Amadeus is a technology company that runs the behind-the-scenes computer systems many airlines use for bookings, check-in, boarding, and baggage.

The company has been referred to as the Information Technology (IT) 'backbone' for airlines for many airlines, including British Airways, Lufthansa Group airlines, Air France, Qatar Airways, Cathay Pacific and Southwest.

Cyril Tetaz, an Amadeus executive, told Simply Flying in 2022: 'We're essentially the IT backbone that helps passengers engage with the airline throughout all the touchpoints that the airline wants to use.'

'Whether they're going to use [the airline's] website or connect through a travel agency, book a ticket, or got to the airport and get a boarding pass. We're essentially the primary passenger system provider from the moment when the [flight] offer is made to the moment that the offer is delivered at the airport.'

The system disruptions appeared to peak around 8.50am, with Downdetector saying incidents of passengers having technical difficulties began dropping off after that.

However, some customers have continued to report problems with the airline's systems over an hour into the outage.

The computer issue led to massive lines among flyers checking into airports, including San Diego, where flyers claimed they were in danger of missing flights despite arriving well before boarding time.

Amadeus released the following statement regarding the incident: 'Amadeus briefly experienced a technical issue yesterday affecting Southwest Airlines, originating from a third-party technology provider.'

'Our teams took immediate action and worked closely with the provider to restore normal operations. We apologise for any inconvenience caused.'

A similar issue affected United and Delta Airlines on Tuesday, with a United spokesperson noting that their vendor also experienced a technical failure which prevented flyers from using their systems.