Hundreds of flights were cancelled in major airports in the US Pacific Northwest due to icing and snowstorms.
By 8 a.m. Friday local time, Seattle, the largest city in the northwestern US state of Washington, had cancelled 449 flights with 39 per cent of flights leaving the city and 40 per cent of flights coming in, Xinhua news agency reported.
Portland of Oregon had cancelled 202, or 46 per cent of flights leaving and 41 per cent of flights coming in.
A total of 51 flights were cancelled at San Francisco Airport, the largest airport in California's Bay Area. Another 79 flights had been delayed.
Thousands of flights across the US have been cancelled on Friday, snarling holiday travel, as weather conditions worsen ahead of a combination of snowstorms and freezing temperatures set to sweep across two-thirds of the country this weekend.