Will new terminal rejuvenate London's Heathrow?

T5 opens after six years and $8.5 billion.

Lost baggage, long queues, dreary carpets, dim lighting, and miles to the departure gates: Heathrow may be the world's largest international airport, but for the 68 million passengers who pass through each year, there has been little else to coo about.

Until now. The airport that began life more than 60 years ago in a grassy field will be reborn Thursday with a new $8.5 billion terminal that aims to transform Heathrow's image as a place to avoid.

Terminal 5, or T5 as it has become known, is everything that its four aging siblings are not: a triumphant geometry of glass, steel, marble, and hardwood that is light, spacious, and technologically 21st century.

And when the first inbound passengers from Hong Kong step blinking into its cavernous vectors at around 5 a.m. Thursday, they may be forgiven for thinking they have been diverted to one of Heathrow's prouder rivals – Madrid, say, or Charles de Gaulle.

"The terminal is absolutely spectacular," says one airport insider who worked on T5. "You forget you are at Heathrow. It definitely will change the passenger experience."

Simon Calder, a British travel writer, is less effusive. He says Heathrow has much to do to change its image. "It's the gateway to Europe and travelers from North America and elsewhere expect a warm welcome, a smooth transfer, and general absence of stress.

"What they get is the most miserable time. If you get out in a couple of hours and you're on the same plane as your luggage, that counts as a success," he adds. "T5 should transport us into the 21st century, but will only benefit a modest number of passengers. And when the dust settles, Heathrow will still be a challenging place."

In an age when aviation has been closely linked to noise pollution and climate change, expanding Heathrow has proved hugely controversial. T5 was first mooted as far back as 1993 and generated Britain's most protracted public inquiry, which lasted almost four years.

Opposition to airport expansion remains vocal, and hundreds of demonstrators are expected Thursday morning. They are concerned T5 will lead to a new runway, resulting in more flights, more noise, and more pollution.

"For people living under a flight path, with a plane coming over every 90 seconds, there's virtually no escape from the noise," says John Stewart, chairman of an anti-expansion residents group, Hacan. "It's like living under a sky of sound.

He says that of 480,000 flights from Heathrow each year, 100,000 serve destinations where there is a rail alternative. Fittingly, the first flight out of T5 is to Paris, a city just two hours away by rail. "The authorities should limit landing slots for these short-haul flights," Mr. Stewart says.

The company that runs Heathrow (and six other British airports), BAA, makes no secret that T5 is just the beginning of a regeneration that it hopes will culminate in a third runway and sixth terminal. Half the Heathrow passenger throughput – about 30 million people a year – will now pass through this new "gateway to Britain," leaving scope to tear down old terminals and rebuild them in T5's image.

Mary Kearney, a BAA spokeswoman, notes that the 45-million-person capacity airport has been straining to handle 68 million travelers a year. "But now half the airport population can migrate to T5 and we have the space to undertake major development," she says.

Ainhoa Alvarez, who uses Heathrow regularly for business and leisure travel, says it's about time Heathrow got a face-lift. "In Terminal 3, the ceilings are really low," she says. "If you're like my husband, you're almost touching the ceiling, and it's a horrible place if you have to be there for a little while. It's just not what you expect when you come to London, especially if you compare it to Madrid or Hong Kong."

T5 is one superlative after another. It was Europe's biggest construction project, with 7,000 workers on site at times, and took almost six years to complete. Constructed over 260 hectares (642 acres) – slightly smaller than Central Park – you could fit 50 soccer fields into the surface area of its five stories. Yet it is crammed between two of the world's busiest runways and Europe's busiest motorway, the M25.

The 40-meter (131-foot) high canopy, which took a year to hoist into place in six chunks, is Europe's biggest single-span roof. Sixty aircraft stands are located around a "toast rack" of three rectangular buildings.

Eminent British architect Richard Rogers compared it to the Pompidou Center. But then, his company designed it. "It's 19 years of work that is coming to fruition when the first plane comes through," says chief architect Mike Davies.

But it is not just about the design, the acclaimed artwork and sculptures, the tree-planted plaza in front of the arrivals lounge, and the sweeping views, which, on a good day, extend across the runways to Windsor Castle.

BAA also enthuses about technology like the baggage drop, which hoists suitcases to an underfloor belt, enabling passengers to walk forward to departures rather than turning around. "It's on the way, not in the way," quips Ms. Kearney. Or the 10 miles of belts capable of handling 12,000 items of luggage in an hour. Twenty security lanes promise speedier passage, though domestic travelers will now be fingerprinted.

The financial sector, less enamored of BAA since it was taken over by Spaniards 18 months ago, thinks T5 could be a watershed.

"It is a turning point for the Heathrow brand, but there is an awful long way to go," says Howard Wheeldon, an aviation expert at London brokerage BGC Partners. "T5 is the model of the future. If they get it right, then we can at last believe that BAA knows what it's doing – it's learned its lesson and is putting airlines and customers where they should be – at the top of the queue."

Mr. Calder says grandeur isn't everything. "Marseille has a new terminal that is the antithesis of T5," he says. "It's a shed, with only one place where your bags are weighed. It's got everything you need and nothing you don't."