LONDON -- The world's busiest international airport told infuriated passengers not to expect full service until Thursday, five days after a five-inch snow flurry turned hundreds of thousands of holiday plans into a nightmare of canceled flights and painful nights on terminal floors.
Travelers' anger boiled over into politics as Britain's prime minister offered to put troops on snow-clearing duty. Europe's top transport official threatened tougher regulation of airports unable to cope with unusually wintry weather.
As the snow began melting away in much of London, transportation experts said it had revealed both Heathrow and the high-speed Eurostar train to mainland Europe to be woefully unprepared for what may be a period of frigid winters last seen here nearly a half-century ago.
Climate experts said the usual prevailing stream of warm, wet Gulf air is getting blocked and diverted midway across the Atlantic -- and letting cold fronts from the Arctic and Eastern Europe mount a rare prolonged invasion of Western Europe.
When those cold fronts pass over the relatively warm North Sea and Irish Sea, they turn into snow factories of rare power.
Many experts say the frequency of the European cyclical cold-front phenomenon, which dates back to 18th-century weather records, is actually declining in an age of climate change. However, global warming can lead, counterintuitively, to more powerful winter storms because of higher volumes of moisture in the air.
"The 1960s was a a 5- to 10-year period of extreme weather, hot and cold. We could well be going into such a period and my advice would be prepare for it," said Sir David King, former chief scientific adviser to the British government, who is now director of the Smith School of Enterprise and the Environment at Oxford University. "The risk to our economy is significant if this happens and we're not prepared."
Aviation consultant Chris Yates said that after many years without heavy snowfall, short-term thinking and underinvestment had left Heathrow and dozens of other airports across Britain and Ireland without enough equipment or personnel to cope with big storms.
"They have concluded they don't need snow clearance equipment, so we don't have the capability when bad weather comes in," he said.
He said airport operators in Helsinki, Stockholm and other snowy climes have the equipment and manpower to clear runways within 30 minutes and to remove ice and snow from aircraft stands quickly, while Heathrow lags far behind.
This could be seen in the days after Saturday's snow, when airports in Frankfurt, Prague, Amsterdam and other major cities in mainland Europe bounced back more quickly than Heathrow, where the ice quickly hardened, making removal more difficult. London's Gatwick was hit by less snow and recovered more quickly than the larger Heathrow, with its runway open Tuesday night and flights operating.
European Union transportation commissioner Siim Kallas threatened the possibility of new "minimal service" standards for airports if performance does not improve.
"Better preparedness, in line with what is done in Northern Europe is not an optional extra, it must be planned for and with the necessary investment," he said.
Prime Minister David Cameron said his government had "offered military assistance" to the company that operates Heathrow, BAA, which said it was grateful for the offer but didn't need the help.
It said, however, that while the second of two runways reopened late Tuesday, officials needed "breathing space" to clear remaining snow, restart equipment and move planes and crews back into place. They will thus will be operating around one-third of a normal flight schedule until 6 a.m. on Thursday.
"It's pathetic -- you would think this is a Third World country," said Janice Phillips, 29, trying to get back to Minneapolis and sitting next to her sleeping boyfriend, head propped up on a backpack with his mouth ajar. "I've been here for two weeks and all they've been talking about was this snow forecast. You would think the government could do a better job."
Eurostar, which runs through the $18 billion construction of the Channel Tunnel, also could not cope, advising passengers throughout the day to cancel and stay home.
To compound the problem, bedraggled passengers said they received little information about their options, if any, and many were forced to wait outside in the cold because terminals were packed. Many slept on filthy terminal floors.
Outside London's Eurostar terminal, the line of travelers waiting for trains snaked several hundred yards (meters) down the street from the station.
Inside, puffy-eyed passengers shuffled across the cold concourse, watching anxiously as the line periodically spurted forward. One older man played Beethoven's "Ode to Joy" on his harmonica. The crowd livened up when he switched to Europe's "The Final Countdown."
By Tuesday evening Eurostar said it expected to operate a nearly normal schedule the next day but said passengers who'd missed previous trains wouldn't be able to travel.
Eurostar said trains were running with speed restrictions in both England and France as a precaution because of the snow.
Rail expert Christian Wolmar said Eurostar was being cautious after holiday-season breakdowns last year, when powdery snow got sucked into the engines of speeding trains, and the entire Eurostar service was suspended for three days after trains got stuck in the Channel Tunnel. A report recommended running trains more slowly in snow.
Wolmar said the real problem was bad management.
"Eurostar ought to be ashamed of themselves," he said. "It would seem possible to put on extra trains, but they can't get the crews or they can't get the trains in place .... it's inexplicable."
The icy road conditions also forced many other major businesses in the UK to stop taking online orders for pre-Christmas delivery.
Paris, like London, was overwhelmed by snow twice in the last few weeks, with a few centimeters effectively paralyzing roads in the French capital and surrounding highways, shutting down the entire Paris bus system and canceling or delaying flights from the busy Charles de Gaulle and Orly airports.
Amsterdam's Schipol airport suffered on Saturday when all but one runway was closed after receiving about 10 inches of snow, forcing the airport to borrow 3,000 cots from the Red Cross to aid passengers, but it reopened fully the next day after all the runways were cleared by 450 airport personnel working in snow squads round the clock.
Problems persisted in Germany at Frankfurt airport, continental Europe's second-largest hub, saw 550 cancellations out of a total of about 1,300 flights Tuesday because of bad weather conditions.
Problems have mounted badly in Ireland, where intense, sustained snow has snarled traffic and shut down the country's major airport north of Dublin. Dublin Airport officials said the intensifying snowfall meant they couldn't keep runways free of ice.
Air France-KLM President Pierre-Henri Gourgeon said snow-related disruptions over the weekend cost the airline €15 million to €20 million ($20 million to $27 million), while losses for the entire month could reach €35 million ($47 million).