BRITISH Airways has apologised to passengers for delays after an IT glitch hit check-in systems today.

Angry travellers complained of hours queuing at airports but the airline said it is not a worldwide problem as some passengers had described it.

A spokeswoman confirmed passengers are being checked in at Heathrow and Gatwick airports but said the process would be "a bit slower than usual".

Asked where the IT problems are, the spokeswoman said: "It is patchy."

Responding to passengers on Twitter, the airline wrote: "We apologise to our customers for the delay and we appreciate their patience as our IT teams work to resolve this issue."

It added: "Our colleagues are doing everything possible to check in customers for their journey."

Ewan Crawford, of Glasgow, who was waiting at Chicago O'Hare International Airport for a flight to Heathrow, tweeted: "Never a good sign when they deliver water to the gate! Waiting at ORD for @British_Airways 296. Worldwide computer outage apparently! Hmm."

Matthew Walker, another passenger hoping to fly from the US to London, said he had been waiting for more than two hours to board his flight at Seattle Airport.

The 29-year-old financial analyst, who lives in London but is originally from Australia, checked in online before arriving to catch his flight but said staff on the ground could not access their computer systems to see which passengers had gone through security.

Speaking from the airport, he said: "People were lining up, some had already checked in and got through security, but others, when this thing happened, whatever it is, were stuck in the check-in queue.

"So they (the staff) have the problem that they didn't know who had already gone through the gate because all the systems literally just had a meltdown, basically."

Passengers at Heathrow Terminal 5 reported waits of about 45 minutes to check in.

Elaine and Paul Barnett, who had come from Sheffield to travel to Sardinia, said the process had taken "longer than usual" and they had been required to give extra details once they reached the desk.

"You really have to get here early and expect that it's busy," Ms Barnett said.

Earlier problems appeared to have been smoothed out by early morning, with most queues moving.

Patrick Darby, from Dulwich, who was travelling to Russia, said: "There was a hold-up when nothing seemed to happen but that has eased up now."

In July BA had to apologise after a glitch in its new check-in system caused delays.

The airline began installing the system at airports across the world in October last year and the roll out was completed earlier this year.

On the latest issues, BA said in a statement: "We are checking in customers at Heathrow and Gatwick Airport this morning as normal, although it may take longer than usual.

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