Heathrow Airport, the world's busiest international air hub, faced a torrent of criticism Tuesday after it cancelled more than 700 takeoffs and landings, continuing snarls that began with a weekendsnowstorm that arrived at the height of holiday travel season.

Heathrow's operational problems have frustrated travelers and airlines in part because there has been little significantadditional snow since an official measurement of 9 centimeters (3.5 inches) at the airport Saturday. But that storm, and the cold and ice that followed, have crippled the airport since then and thwarted holiday plans for thousands of travelers.

With Christmas looming, Heathrow, privately owned and operated by Ferrovial SA's BAA Airports Ltd., attempted Tuesday to clear the snow and ice and cope with its backlog of cancelled flights. In a statement Tuesday, the airport said that until 6 a.m. on Dec. 23, it would be operating only one-third of its flightschedule.

On Tuesday, Heathrow cancelled 752 flights -- 389 arrivals and 363 departures -- out of 1,300 flights that usually pass through airport on a busy day, a spokeswoman for the airport said. Gatwick cancelled 50 flights Tuesday out of 695 scheduled, according to a spokeswoman.

Since the snow began Saturday, Heathrow has cancelled about 3,200 flights, or more than 60% of its total flightschedule, whereas Gatwick has cancelled about 25% of its scheduled flights, according to statistics provided by the respective airports.

At Heathrow, part of the problem is that the airport operates at near full capacity, about 98%, a spokeswoman for the airport said. That leaves little time to clear the runway between flights and creates a particularly bad knock-on effect when there are cancellations.