Thousands of others were stranded at the airport, with no hotel accommodations available and with concessions running low on food and supplies.
Departure gates turned into impromptu camp sites, as miserable passengers slept on the floor, surrounded by luggage.
"This is crazy. There's nowhere to sit - you have to sit on the floor," said one stranded traveler at the height of the crush. "It's just crazy, crazy."
At least three airlines cancelled all flights for the remainder of the day Sunday, including Alaska Airlines, Horizon Airlines and and JetBlue, due to deteriorating conditions.
Other airlines had more cancellations than departures. Some passengers were told they may be stuck at Sea-Tac until Christmas Eve or even Christmas Day.
"It's just frustrating knowing that we were supposed to be home, and now we can't go," said one traveler. "You're just kind of helpless - it's a helpless situation. Its frustrating for families, and I just feel bad for everybody here, too."
The disruptions were too much for some beleaguered passengers, who broke down into tears amid the chaotic conditions.
"They've canceled my flight. So I'm trying to find another way out and trying to reclaim the luggage that was supposed to be checked though," said another frustrated passenger.
And there was no use trying to get out by train or bus - all Amtrak train service was shut down in the Pacific Northwest as well, and local transit agencies were cancelling many routes.
Thousands of people arrived at Sea-Tac on Saturday and Sunday only to learn that their flight had been cancelled, then couldn't find a hotel room or transportation back home.
|Passengers wait on long lines at a security checkpoint at the Seattle-Tacoma International Airport. (AP Photo/Seattle Post-Intelligencer,Karen Ducey)|
Hundreds of stranded passengers were camped out on the floor at departure gates, sleeping wherever they could find a spot.
At 3 p.m., Alaska Airlines and Horizon Air suspended service to and from Portland, Ore., and Seattle for remainder of the day due to severe winter weather and deteriorating conditions at both airports.
Airline officials said the snow and freezing rain that hit the region starting last week have severely impacted the airlines' operations.
"We regret the impact these cancellations are having on our customers' holiday travel plans," Alaska Airlines' chief operating officer Ben Minicucci said in a statement.
Many other airlines were cancelling flights as well.
Travelers are advised to contact their airline for flight status and to attempt to rebook from home, if necessary. Sea-Tac Airport's flight status page appeared to be overloaded and failing to respond Sunday morning, so travelers should check their flights on the individual airline web sites.
"There are very long lines at the ticket counters and airline agents are overwhelmed," said Sea-Tac spokeswoman Terri-Ann Betancourt. "It will be quicker and more efficient to rebook travel arrangements before arriving at the airport."
Airport concessions are having trouble getting deliveries, anyone coming to the airport should come prepared with extra food and other essential supplies, officials said.
Unusual easterly winds, which hit the runways from the side, are the main culprit affecting flight arrivals and departures, Betancourt said.
"When the winds decrease, flights are expected to resume and airlines will work to accommodate those who have missed flights," Betancourt said in a prepared statement.
The airport's cell phone lot also remains closed.
"Allow extra travel time, given roadway conditions in the region, and bring your patience to the airport," Betancourt said.
Interstate 90 at Snoqualmie Pass was shut down Saturday night and remained closed Sunday until noon due to blowing snow and deep drifts along the freeway.
Travel on many other major highways throughout the region is difficult due to snow and ice on the road. Drivers should check their route before heading out.
King County Metro
About half of the scheduled bus service was cancelled for Sunday.
In order to safely transport as many passengers as possible, Metro is focusing on providing bus service on cleared highways and arterial roads, and to major transit centers and park-and-ride lots that normally have Sunday service. (See latest Metro status reports)
As of early Sunday morning, Metro plans to offer its Seahawks shuttle service to Qwest Field from Eastgate Park-and-Ride in Bellevue, Northgate Park-and-Ride in North Seattle, and the South Kirkland Park-and-Ride.
These shuttles will begin service at approximately 11 a.m. Fans should expect crowded conditions on the shuttles, and should give themselves plenty of time to get to the game because the buses may be delayed by road and traffic conditions. Another transit provider handles service from the Federal Way and Kent park-and-ride lots, and does expect to provide shuttle service from those locations today.
For regular Metro service on Sunday, passengers should be prepared to board buses at major transit centers, flat arterials, or at the top or bottom of hills. Please dress warmly, wear appropriate footwear, and be prepared to wait. The buses that are running could be significantly delayed by road and traffic conditions.
Amtrak train service
BNSF Railway has closed its many of its trracks in the Northwest, leading the cancellation of Amtrak trains in the Pacific Northwest.
The Cascade Service, Empire Builder, Coast Starlight are all cancelled on Sunday.
BNSF Railway has informed Amtrak that normal passenger train service to and from Seattle cannot be operated due to infrastructure issues and weather conditions.
There is no service for the entire Amtrak Cascades route between Eugene, Ore., and Vancouver, B.C. No alternate transportation is available, due to the weather conditions.
No service for Empire Builder Trains 7 & 8 route segment between Seattle and Spokane, Wash. Both Trains 7/27 & 8/28 will originate and terminate in Portland, Ore., with no alternate transportation available between Seattle and Spokane. No alternate transportation available between Seattle and Portland.
Coast Starlight Trains 11 & 14, which operate daily between Seattle and Los Angeles, will operate for the full route, subject to extreme delays.
Amtrak regrets any inconvenience. This information is correct as of the above time and date. Information is subject to change as conditions warrant. Passengers are encouraged to call 800-USA-RAIL or visit Amtrak.com for schedule information and train status updates.