Passengers queue at check-in desks at Terminal 5 at Heathrow airport in London

London's Heathrow Airport, the busiest in Europe, is failing to meet targets on waiting times for passengers clearing passport control in its new Terminal 5 building.

BAA, which is owned by Spanish construciton giant Ferrovial, said Thursday that 1 in 4 non-EU passengers had to wait longer than 45 minutes to move through passport control and immigration queues last month, based on Border Force data, missing targets on 23 of the 30 calendar days last month.

UK Home Office targets suggest a wait time of no more than 45 minutes for non-EU passport holders and 25 minutes for UK and EU nationals.

BAA added that delays were also evident in other Heathrow terminals, including a 15 percent target miss in Terminal 4, where passengers were forced to queue for more than 3 hours Monday, according to several reports.

IAG chief executive Willie Walsh said Wednesday that he and his rivals would be prepared to pay higher landing fees, if necessary, to trim waiting times at Heathrow, telling BBC radio the situation was near "crisis" levels.

Last month, the British Transport Association, which represents 11 domestic and international carries, wrote to the Home Office complaining that stricter enforcement of border controls were contributing to the delays.

"Immigration waiting times during peak periods at Heathrow recently have been unacceptable and we have called on the Border Force to address the problem as a matter of urgency," BAA said in a recent statement.

Heathrow moves more than 70m passengers each year through it five terminals, an average of almost 200,000 each day, and is running 99 percent capacity. The British government has axed plans for new runways and airports in the face of heavy lobbying from both the airline industry and various environmental groups.

The recent delays, however, will raise broader questions about London's level of preparation for this summer's Olympic Games, which, along with the Paralympics, is likely to attract 500,000 extra passengers, according to Britain's airspace controller NATS. With nearly 20,000 athletes in both competitions - and untold pieces of luggage, kit and sporting implements - BAA predicts nearly 200,000 pieces of luggage will be handled at Heathrow at the peak of the Games.

Virgin Atlantic, the airline owned by billionaire Richard Branson, warned UK Home Secretary Theresa May in March of a "significant risk of severe delay and disruption" at London's airports during the sporting jamboree. May has told Parliament that the government will add extra immigration staff to handle the increased traffic.