Long waits to clear passport control at London Heathrow Airport can depend on which way the wind is blowing, Britain's immigration minister said on Tuesday.
Delays at the world's busiest airport for international passenger traffic have triggered a furore in Britain as the clock ticks down to the 27 July opening of the London Olympics, for which Heathrow will be the main gateway.
Immigration Minister Damian Green said passengers from New York might well have to wait longer to clear passport control if their flight arrives 10 minutes after one from Lagos in Nigeria, for example, rather than 10 minutes before.
"That will depend on the wind, over which, with the best will in the world, airlines and the Border Force don't have the control," he told a parliamentary committee.
BAA, the airport's owner and operator, said some passengers had to wait up to three hours to get through Heathrow Terminal 4 last month.
Green said the queue lengths seen at some times of the day at Heathrow were "unacceptable".
Home Secretary Theresa May and Transport Secretary Justine Greening updated the cabinet on the efforts to tackle the delays.
"We are working to improve the efficiency of the Border Force so we get better at managing queues," Prime Minister David Cameron's spokesman said afterwards.
"It is going to take some time."
He said plans were in place to cope with the Olympic surge of passengers, but added: "We are confident that our plans are robust, but... it is an exceptional period and there will be some disruption."
British actress Joan Collins blasted May after being held up at Heathrow on Tuesday.
"1000s waiting at passport control - listen up Ms. May - need more officers!" the 78-year-old former "Dynasty" star said on Twitter.