Ahead of Hurricane Sandy's landfall in the U.S., the storm already is causing widespread disruptions for millions of travelers, with thousands of flights canceled, mass transit shutdowns in New York, New Jersey, Pennsylvania, and Washington, D.C., and Amtrak cancellations across the Northeast.
More than 10,000 flights were canceled through Tuesday, according to FlightAware.com, and that number is expected to grow into Wednesday.
The most affected hub was Philadelphia, with 1,220 cancellations scheduled for Monday, FlightAware.com reported. In New York and New Jersey, airports remain open although all flights in and out have been suspended, according to the Port Authority, which is encouraging travelers not to head to the airports.
Airlines abroad have canceled most flights to the U.S., including British Airways and German carrier Lufthansa. Lufthansa expects to resume flights to three U.S. destinations on Tuesday afternoon, but says it is monitoring developments closely, NBC News reported.Video: Hurricane Sandy: Travel delays (on this page)
Major airlines are offering waivers to customers who wish to reschedule their flights without paying the typical fee of up to $150. To cancel a ticket, passengers should call the airline.
Don Morelli, a meteorologist with WSI, a sister company of The Weather Channel, said major flight delays and airport closings were likely to continue through Tuesday.
"The criteria for closing an airport is around 58, 60 miles an hour, which is easily going to be reached for much of the major hubs from D.C. northward to New York City and even into Logan (in Boston)," Morelli said. "Major delays (are) going to be very, very widespread right through mid-week, so [it’s] not a good week to be traveling across the Northeastern U.S."
Airlines started moving planes out of airports in the Northeast to avoid damage.Video: Millions hunker down ahead of Hurricane Sandy (on this page)
At 8 a.m., the National Hurricane center said Sandy was centered about 265 miles southeast of Atlantic City and about 310 miles south-southeast of New York City.
Subway, rail service halted
New York Gov. Andrew Cuomo on Sunday ordered New York City's transit service to suspend bus, subway and commuter rail service in advance of the massive storm.
The subway system started shutting down shortly after 7 p.m. on Sunday. Stations now are boarded up with sandbags on top to make sure that no one can enter the platforms. The last buses ran at 9 p.m.
"The transportation system is the lifeblood of the New York City region, and suspending all service is not a step I take lightly," Cuomo said. "But keeping New Yorkers safe is the first priority, and the best way to do that is to make sure they are out of harm's way before gale-force winds can start wreaking havoc on trains and buses."
Video: Roker: Up to 11-foot storm surge expected (on this page)
The city's mass transit system is the nation's largest. The subway alone has a daily ridership of more than 5 million.
"This storm will batter the MTA, but the precautions we take now will allow us to recover much more quickly," said MTA Chairman and CEO Joseph J. Lhota.
The Metro-North Railroad, which runs service between New York City and its northern suburbs in New York and Connecticut, and the Long Island Rail Road also suspended train service.
"Subway and railway stations will be closed after the last trains," the MTA said in a statement.
There is no timetable for the restoration of service.
"Service will be restored only when it is safe to do so, after careful inspections of all equipment and tracks. Even with minimal damage this is expected to be a lengthy process," said an MTA statement.Interactive: Hurricane Tracker (on this page)
East River ferry service was suspended, and the Staten Island Ferry was also scheduled to stop running, New York Mayor Michael Bloomberg said in a press conference Sunday.
New Jersey Gov. Chris Christie ordered all of the state's bus, rail and light rail to begin a gradual shutdown at 4 p.m. ET, continuing through 2 a.m. Monday. The Atlantic City Rail Line was also suspended.
In northern New Jersey, PATH train service and stations shut down at 12 a.m. Monday.
The Southeastern Pennsylvania Transportation Authority (SEPTA) suspended its service at about 12:30 a.m., and anticipated the shutdown would last through Monday.
The D.C. Metro also suspended service on Monday and gave no indication of when it would reopen.
Amtrak announced that almost all its Northeast corridor services were cancelled on Monday, including Acela Express, Northeast Regional, Keystone and Shuttle services. Additionally, Empire Service, Adirondack, Vermonter, Ethan Allen and Pennsylvanian train services are also suspended, along with overnight services to and from the East Coast, according to a press release.
Amtrak said in a press release that passengers who have paid for their tickets but choose not to travel due to the service disruption can receive a refund or a voucher for future travel. Some tickets booked online that have not yet been printed can be modified or canceled, the press release said.
Amtrak said they will be contacting passengers who have provided information in their reservations, but encouraged customers to monitor alerts on their website.
NBC News' Becky Bratu and Tom Costello and the Associated Press contributed to this report.