An employee signals a plane out of the gate at Ronald Reagan National Airport outside of Washington on Tuesday, November 26. A colossal storm system that began in California threatens to wreck Thanksgiving travel plans all the way to the Atlantic this week. 
Travelers wait in security lines at Reagan National Airport on November 26. 
Vehicles pick up passengers in heavy rain at Reagan National Airport on November 26. 
A pedestrian walks through snow showers along Penn Ave in Pittsburgh on November 26. 
Mark Swigart uses a leaf blower to remove snow from the sidewalks November 26 in Pittsburgh. 
Holiday travelers make their way to their car on November 26 after arriving at Pittsburgh International Airport. 
People walk in the rain through Union Square in Manhattan on November 26. New York was bracing for severe weather as the storm made its way east. 
Employees at Dallas-Fort Worth International Airport de-ice a plane before departure on Monday, November 25. 
A fallen tree is removed from a car in Odessa, Texas, on November 25. 
A plow and sanding truck heads up Paseo del Norte in Albuquerque, New Mexico, on Sunday, November 24. 
Cars slide on Paseo del Norte in Albuquerque on November 24. - Storm making it harder on planes and automobiles
- The storm bumped thousands of flights off of their schedule travel times Tuesday
- Amtrak is using the wintry weather to market to passengers
Are you in the grips of the wintry storm sweeping across the country? Please share your videos, pictures and stories at iReport.
(CNN) -- A strong storm struck much of the eastern United States on Wednesday, complicating holiday travel plans for many of the 43 million Americans who filled the nation's highways, airports, and train and bus stations.
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By morning, delays were reported at airports in Philadelphia, Boston and New York.
Heavy winds at New York's LaGuardia Airport resulted in delays for arriving flights of nearly an hour, according to the Federal Aviation Administration.
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Killer storm claims lives across the US Departure delays from Philadelphia International Airport averaged nearly two hours.
Snow blanketed parts of the Midwest, where crews scrambled to clear roads. The storm was blamed for scores of accidents.
Up to a foot of snow was expected in parts of western New York and Pennsylvania.
The storm bumped more than 6,000 flights off schedule and forced 271 cancellations Tuesday. Early Wednesday, another 95 flights were canceled.
"I was very happy I booked the day I did," passenger Harold Rothman said. "Because if I booked tomorrow, I'd probably be delayed."
On Tuesday, low clouds and heavy rain delayed one in three flights -- 678 in all -- from Atlanta's Hartsfield-Jackson International Airport, the nation's busiest. On average, passengers were delayed nearly an hour.
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"Let's face it: With 80% of our airplanes touching the congested Northeast, we're acutely aware that things can go wrong relatively quickly," JetBlue COO Rob Maruster told CNN affiliate WCBS in New York.
If flight delays and cancellations pile up, they could cause a chain reaction throughout the country, as connecting flights outside the Northeast wait for arrivals from the stormy region.
Trains
Amtrak reported no major delays systemwide. It expected to carry about 140,000 passengers, double its normal volume for a Wednesday.
Using the weather as a marketing tool, the nation's rail system was adding seats on some routes.
"Rail travel remains one of the most reliable and comfortable transportation options, especially in weather conditions that negatively impact other modes," Amtrak said.
There may be something to that.
"QUIET CAR. Window seat. Polite seatmate. I have hit the Amtrak travel trifecta. #blessed," Ellie Hall tweeted early Wednesday.
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Automobiles
Road conditions were not great in much of the Northeast.
"It's sleet; it's rain; it's 31 degrees. It's ugly out there," CNN meteorologist Chad Myers said.
Last week, 12 people died, most of them in car crashes, when one of the fronts making up the current storm iced roads from the Rockies to Texas and Oklahoma. More than 100 vehicles ended up in wrecks.
"I get on the highway, and the next thing I know I'm spinning," said Seqret Watson, among the dozens of drivers in Northwest Arkansas sent sliding when their cars hit icy bridges and roads.
"I try to grab my wheel and then I just hit the wall. Just jumped out to make sure my kids were OK," Watson told affiliate KFSM.
The Peterson family had initially planned to drive from Northern Virginia to Massachusetts. But after seeing the forecast, they booked seats on a flight at the last minute.
"It was a small fortune," Jennifer Peterson told CNN affiliate WUSA. "We could've gone to the Bahamas for what we paid!"
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CNN's Dave Hennen, Alexandra Field and Greg Botelho contributed to this report.
