Terminal Five, which cost £4.3 billion (S$12 billion) and is the first addition to Heathrow in 20 years, was inaugurated by Queen Elizabeth earlier this month.

Yesterday, the first flight to land was from Hong Kong, and while the British Airways aircraft landed 10 minutes ahead of schedule, some passengers reported delays while signs were also criticised.

'It took an hour for our bags to come through from the time we landed,' said Mr Mike Salinger, who had travelled from Hong Kong.

'There seems to be no proper meeting point and it seems difficult for people being picked up to be found. The signs don't seem to be very clear,' he added.

Terminal Five, which has been 15 years in the planning and construction, will be able to handle 30 million passengers a year.

Heathrow, used by 68 million passengers a year, is already one of the world's biggest airports, but for years has been plagued by overcrowding in its hotchpotch of ageing buildings due to soaring demand for air travel.

Some passengers were impressed. 'It all seems very efficient. Everything is positive,' said Mr Andrew Fensome, 37, who also arrived on the first flight.

But Londoner Agar Burton, meeting his wife from the flight, was less positive.

'One of the lifts was not working, the signs are not clear and you're not sure where you are. It doesn't seem very user-friendly,' he said.

Some 250 protesters staged what was billed as a 'flash mob' demonstration against plans for further airport expansion, which include a proposed third runway at Heathrow.

The protesters, who had scheduled the protest in advance rather than spontaneously announcing it as a genuine flash-mob event, stripped off their outer clothes to reveal red T-shirts with the slogan 'Stop Airport Expansion'.

Heathrow's logistics director Shaun Cowlam acknowledged the initial difficulties, but said they would be fixed.

'Most airports open with difficulties. Looking at where we are now - is it perfect? Not in every respect,' he said, but added: 'I would say so far, so good. I am cautiously optimistic.'

AGENCE FRANCE-PRESSE