The European Commission on Tuesday blasted the "unacceptable" travel chaos caused by heavy snowfalls this week and summoned airport officials to a meeting to explain themselves.

"I am extremely concerned about the level of disruption to travel across Europe caused by severe snow. It is unacceptable and should not happen again," European transport commissioner Siim Kallas said in a statement.

Kallas said he would convene a meeting with airport officials in the coming days to get more explanations and "take a hard look" at what is needed to ensure they can operate more effectively during winter weather in the future.

"Airports must get serious about planning for this kind of severe weather conditions," he said.

"We have seen in recent years that snow is Western Europe is not such an exceptional circumstance," Kallas said.

"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."

The European Union transport chief said the commission would be ready to propose legislation next year if needed to ensure that airports meet minimum service requirements.

"First I want to hear the views of the airport operators and the different practices in place across Europe. We must look at the issue across the whole travel chain and make sure possible loopholes and weak links are identified and closed," he said.

Thousands of holiday travelers have been forced to sleep at several European airports and train stations in recent days as authorities struggled with an onslaught of snow and ice ahead of Christmas.

On Tuesday, London Heathrow, Europe's busiest airport, was only operating about a third of its normal schedule during a fourth day of disruption, while Frankfurt halted all flights after a new blanketing of snow.

Kallas said the commission, the EU's executive arm, was monitoring the situation very closely and was in constant touch with airlines, airports, rail operators and national authorities in charge of passenger rights.

"In recent days, I have become increasingly concerned about the problems relating to the infrastructure available to airlines -- airports and ground handling -- during this severe period of snow," Kallas said.

"It seems at this stage that this is a weak link in a chain which, under pressure, is contributing to severe disruption," he said.

Statement by Vice President Kallas on air travel disruption across Europe

Statement on the air travel disruption across Europe by European Commission Vice President Siim Kallas responsible for Transport.

I am extremely concerned about the level of disruption to travel across Europe caused by severe snow. It is unacceptable and should not happen again.

Of course, safety of travel comes first and foremost, so there can be no compromise on that front. And extreme snow and extreme weather conditions are and have to be taken into account in contingency planning is which is the responsibility of Member States. They are taking those responsibilities very seriously.

The European Commission is monitoring the situation very closely and is in constant touch with airlines, airports, rail operators and national authorities responsible for passenger rights.

In recent days, I have become increasingly concerned about the problems relating to the infrastructure available to airlines – airports and ground handling - during this severe period of snow. It seems at this stage that this is a "weak link" in a chain which, under pressure, is contributing to severe disruption.

I intend to convene a meeting with airports representatives in the 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 in the similar situations in the future

Airports must "get serious" about planning for this kind of severe weather conditions. We have seen in recent years that snow is 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.

We need to ensure that, from infrastructure providers such as airports and rail infrastructure manages, there are appropriate service levels and minimum quality requirements that are followed and delivered . If there is a need for support from the European Commission in terms of regulation on minimum service requirements for airports in this area, I am prepared to do that, for example, when we bring forward the Airports package on slots and groundhandling which is foreseen before summer next year.

First I want to hear the views of the airport operators and the different practices in place across Europe. We must look at the issue across the whole travel chain and make sure possible loopholes and weak links are identified and closed.

At this time, it does not seem to be an issue for the airlines as they want to fly, fly safely and do all they can as well caring for the passengers. What is necessary is that the expectations from everybody must be reasonable and proportionate.

Finally, when it comes to passenger rights, Europe has put in place a safety net of rights designed to help passengers in cases of difficulties with issues such as overbooking or cancellations. Since early this year, that safety net of rights also covers rail passengers, and in the future will extend to ship, inland waterways bus and coaches. What we need for the future is to make sure that there is proportionate responsibility and risk sharing between all the operators in the supply chain, in particular when it comes to air travel, and this includes also passengers. I intend to address this issue during next year.