London's Heathrow airport canceled 260 flights — about 20 percent of its usual schedule — on Sunday because of snow and low visibility, causing a third day of misery for travelers.
Flights have been disrupted since Friday at Heathrow, one of Europe's busiest airports, which has seen long lines and stranded passengers camping out on its terminal floors.
Heathrow said it had spent millions to improve its ability to cope with icy weather after the airport was virtually shut down by snow for several days in December 2010. But it said that unlike airports with spare runway capacity, it could not space out aircraft during low visibility without causing disruptions.
"Because Heathrow operates at almost full capacity, there is simply no room to reschedule the delayed flights," it said in a statement.
The airport said more cancellations are planned, as forecasters say snow is expected to blanket Britain in the coming week.
Heathrow plans to reduce Monday's flight schedule by at least 10 percent, and it warned that more flights could be canceled if weather conditions at other European airports worsen.
In Germany, icy weather forced Frankfurt airport, Europe's third-busiest, to cancel nearly 292 flights on Sunday.
Gatwick, London's second-busiest airport, said it was operating a normal service Sunday with some delays.