Heathrow, the world's busiest two-runway airport, has defended itself after cancelling 260 flights today due to snow and poor visibility, 20% of its usual schedule.
The airport came under fire from angry passengers who camped out on its terminal floors for a second day yesterday, complaining not enough was done to share information and get traffic moving.
It was far from the first time the airport had drawn criticism for grounding flights.
In December 2010, snow and freezing temperatures virtually closed the west London airport and an inquiry was ordered by its operator BAA into why it struggled to cope.
A panel of experts from airports and airlines across the world were consulted and Heathrow implemented improvements with £36 million pumped into its Winter Resilience Programme.
The money was spent on bolstering snow and ice clearing equipment and increasing staff levels.
In 2010, when Christmas was ruined for thousands of passengers because of wrecked travel planes, the airport had 61 snow clearing vehicles - it now has 130.
The figure includes 10 runway sweepers, 26 tractor ploughs and 19 specialist de-icing vehicles.
The investment also covered an increase in manpower, boosting it from 117 to 510 employees per shift to support Heathrow's "snow plan".
Airport bosses said they also increased the amount of de-icer by 20% to 1.8m litres for the airfield - which would last five days - and 1.3m litres for the aircraft.
Today, a spokeswoman for Heathrow said the airport was coping well after giving advance notice of cancellations.
The issue, she said, was reduced visibility which meant more distance was needed between flights.
She said: "The runways are open and everything is fine at the moment because passengers have had more time to check flights with their airline.
"In 2010, the airport was almost completely closed for several days. This is not the same at all.
"We took a lot of learning from 2010 and invested heavily."
Billy Payne, a forecaster with Meteogroup, the Press Association's weather arm, said: "Visibility is fairly low where the snow is falling, down to about 1.9 kilometres.
"It is reduced visibility but it is not at fog levels although it may drop further if there are heavier bursts of snow."
A spokeswoman for Gatwick Airport said 600 flights were scheduled this morning and none had been cancelled.
The airport has spent £8m on new snow equipment since the big freeze in 2010.