The European Union has heavily criticised European airports for failing to deal with recent freezing weather, which has left thousands of travellers stranded. European transport commissioner Sim Kallas urged airports to get serious about planning, and labelled them a weak link in the infrastructure.In a statement, Mr. Kallas said that airports in Western Europe needed to learn from their counterparts in northern Europe. He said he intended to meet airport officials from around Europe to take a hard look at how they can operate more effectively in the future. Hundreds of flights have been cancelled in recent days, as snow and ice have disrupted travel across Europe. London's Heathrow has been the one of the hardest-hit airports.