LONDON, England

Britain’s prime minister offered troops to help clear airport delays on Tuesday and Europe’s top transportation official said the failure to keep flights operating in winter weather was unacceptable, as exhausted and outraged passengers struggled to get home for the fourth day.

Prime Minister David Cameron said his government had “offered military assistance” to the company that operates Europe’s busiest airport and others in Britain. Heathrow said it was grateful for the offer and didn’t need the help, but still would be unable to restore full service until at least Thursday morning.

“We currently have over 200 volunteers supporting our passengers in the terminals and we have also engaged our construction contractors to assist with the clearance of snow around the airport,” a spokeswoman said.

Cameron said that given the exceptional weather, which saw 5 inches (13 centimeters) of snow fall in an hour on Saturday, it was inevitable Heathrow would shut for a time.

“I am frustrated on behalf of all those affected that it has taken so long for the situation to improve,” Cameron said. He promised the second runway at London’s Heathrow would reopen within hours. But with a backlog of canceled flights, Heathrow said it would be operating around one third of a normal flight schedule until 6 a.m. on Thursday.

An airport spokeswoman said officials needed “breathing space” to clear remaining snow, restart equipment and move planes and crews back into place.

Major delays and cancellations also disrupted other European airports and the Eurostar train link, leaving thousands stranded across Europe as Christmas approached. The icy road conditions in much of Britain also raised doubts about the delivery of Christmas gifts because many side roads were hazardous.

“We are delivering as much as we can, but inevitably some things may not be delivered before Christmas,” said Anina Castle, spokeswoman for the Currys chain, which sells computers, iPods, home appliances and many other items.

Currys and many other major businesses have stopped taking online orders for pre-Christmas delivery because of the poor road conditions.

Transportation Commissioner Siim Kallas said new airport regulations due to be published before the summer could include new requirements on “minimal services” airports will have to be able to provide during severe weather.

He said he will meet with airport representatives in coming days “to ask for further explanations and to take a hard look at what is necessary to make sure they would be able to operate more effectively.”

“Airports must ‘get serious’ about planning for this kind of severe weather conditions,” Kallas said. “We have seen in recent years that snow in Western Europe is not such an exceptional circumstance.

“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, particularly on the side of the airports,” Kallas said.

The terminals at Heathrow were clogged with passengers desperately looking at computer screens to see if they would be able to get to their destinations. So many people were sprawled on the floor that it was difficult to walk.

“It’s pathetic — you would think this is a Third World country,” said Janice Phillips, 29, who was trying to get back to Minneapolis.

“It’s not even snowing!” said Candie Sparks, 19, who was trying to get back to Santa Fe, New Mexico. “It’s crazy.”

Air France-KLM President Pierre-Henri Gourgeon said that snow-related airline disturbances over the weekend cost the airline between 15 and 20 million euros. He put the price to the airline of weather-related problems for the entire month of December at 25-35 million euros.

Eurostar, which links England to France and Belgium by train, also advised passengers to cancel their trips in the coming days and receive a full refund unless travel was absolutely necessary. Eurostar said trains were running with speed restrictions in both England and France as a precuation, because snow and ice stirred up by trains could damage the underside of the carriages.

Outside London’s Eurostar terminal, the line of travelers waiting for trains snaked several hundred meters (yards) from the station, down the street and all the way to the British Library.

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.”

On the rails, Eurostar trains were still operating at reduced speed, with at least one high-speed train crawling along at 20 kilometers per hour (12 miles per hour) inside the Channel Tunnel.

Rail expert Christian Wolmar said Eurostar was being cautious after last year’s holiday-season breakdown, when powdery snow got sucked into the engines of speeding trains, and the entire Eurostar service was suspended for three days. A report recommended running trains more slowly in snow.

Wolmar said the real problem was bad management at Eurostar.

“Eurostar ought to be ashamed of themselves,” he said. “They ought to be putting on more trains … but they can’t get the crews or they can’t get the trains in place.”

At Paris’ Gare du Nord station, several hundred passengers waited in an orderly line stretching to the back of the station. Another several hundred lined up at the top of an escalator.

Fresh snowfall forced Frankfurt airport, Germany’s biggest, to suspend takeoffs and landings for a few hours early Tuesday.

In Cologne, two railway workers were killed during the night when they were hit by a train as they tried to de-ice a switch, the German news agency DAPD reported.

Ireland suffered its heaviest sustained snowfall since the winter of 1962-63, snarling traffic and shutting 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.

Thousands of stranded passengers queued for refunds at the ticketing desks of Ryanair and Aer Lingus, while tens of thousands more Irish people struggling to get home in time for Christmas remained on standby worldwide.

Eamonn Hewitt, spokesman for ferry line Stena, says ships on all Britain-Ireland routes were reporting exceptionally high traffic last experienced during the volcanic ash scare in April and May.

———- AP

Photo: Belgium Europe Weather

BRUSSELS, Belgium — A child sleeps on a luggage cart at Zaventem airport in Brussels yesterday. Zaventem airport received a crucial supply of de-icing fluid from France yesterday after a shortage on Monday cancelled flights and threatened to close the airport down. (Photo: AP)