British Airways warned Tuesday that customers could face further delays after a computer glitch in its global check-in system held up some flights, particularly in the United States, for hours.

‘Our IT team are working hard to fix this issue,’ BA wrote on its Twitter page in response to one customer's tweet sent around 0635 GMT.

Contacted by AFP, a BA spokeswoman said passengers gathered at London's main airports would face delays to outbound flights.

‘We are checking in customers at Heathrow and Gatwick Airport this morning, although it is taking longer than usual,’ she said in an emailed response.

‘We would encourage customers to check in online before they reach the airport.’

At Phoenix airport in the United States, Karen Reyburn tweeted: ‘After six hours I am actually sitting on a plane! Excitement!’