New York's LaGuardia Airport is not expected to open Wednesday, due to extensive damage, New York Governor Andrew Cuomo said during a press conference Tuesday morning.
Much of Tuesday's air and rail service has been canceled, and millions of public transit commuters are without service. Here's what to expect in many of the affected areas:
New York City's massive public transit network was crippled overnight.
"The New York City subway system is 108 years old, but it has never faced a disaster as devastating as what we experienced last night," Metropolitan Transportation Authority Chairman Joseph J. Lhoto said in an online statement.
Seven subway tunnels under the East River flooded in the course of the storm, the Metro-North Railroad lost power in sections of its lines, and the Long Island Rail Road sustained flooding in one East River tunnel and evacuated its West Side Yards, according to the statement. The Hugh L. Carey Tunnel flooded "from end to end," the Queens Midtown Tunnel also was closed because of flooding, and six bus garages were disabled.
Lhota said MTA employees will restore service as quickly as possible "to help bring New York back to normal."
In New Jersey, all NJ Transit services remain suspended until further notice. Transit service is also suspended Tuesday in Maryland, according to the Maryland Transit Administration.
Transit officials in Philadelphia said they are optimistic that city and suburban services will be up and running sometime Tuesday but could not give an exact time.
Southeastern Pennsylvania's regional rail commuter lines present a bigger challenge, said SEPTA spokeswoman Jerri Williams. Crews were out overnight and were walking the lines Tuesday assessing damage with the hopes of resuming commuter rail service Wednesday morning.
"But we already know it's going to be a challenge. We already know there's going to be disruptions and delays in the morning," Williams said.
In Boston, most transit service was set to resume Tuesday morning, with some delays, according to the Massachusetts Bay Transportation Authority.
Amtrak extended Northeast Corridor cancellations through Tuesday. Bus routes connected to those trains were also canceled. Trains coming to and from Canada or to and from the South will still operate, but they will stop short of the storm-affected states. Consult Amtrak's website for more details.
Thousands of flights canceled
There have already been more than 15,000 flight cancellations since Sunday as a result of Sandy, according to flight tracking site FlightAware.com.
That number is expected to rise, since FlightAware.com reports that most airports in the New York City area are closed and haven't announced reopening times.
"It is unlikely there will be scheduled flight operations to/from NYC today and some airlines have begun canceling flights on Wednesday," according to a FlightAware.com statement.
There have been 6,047 flights canceled for Tuesday, as of 8:50 a.m., FlightAware figures show. Philadelphia is leading the way with 1,085 cancellations, followed by the New York area airports with nearly 1,000 each.
Airlines have already canceled 635 flights for Wednesday. More cancellations are expected Tuesday and Wednesday as airport staffs assess damage.
Some airline operations resuming
New York's LaGuardia Airport is expected to remain closed through Wednesday due to significant damage. Newark Liberty International Airport is also expected to be closed through Wednesday as engineers assess storm damage, Port Authority of New York and New Jersey spokesman Anthony Hayes said.
If John F. Kennedy International Airport reopens Wednesday, which is unlikely, service will be limited, Hayes said. He strongly advised travelers to contact their airlines before heading to the airport.
Yet there are signs that some of the Northeast's other airports are coming back to life.
On Tuesday morning, Philadelphia International Airport was expecting its first inbound cargo flight since the storm hit, and limited passenger operations are scheduled to begin Tuesday afternoon, said airport spokeswoman Victoria Lupica. Airport parking lots and roads are drivable, she said.
Bradley International Airport, which serves the Hartford, Connecticut, area and western Massachusetts, was gearing up to resume operations Tuesday around noon, said airport spokesman John Wallace. The airport, which was spared the worst of the storm, never lost power and most employees were able to get to work this morning, he said.
Delta Air Lines will resume flying Tuesday at Boston Logan and the major Washington area airports, an airline spokesman said. United previously announced that it hoped to resume service at the major Washington area airports and Cleveland on Tuesday evening, weather permitting.
Most carriers will allow affected passengers to change their itineraries without penalty. You can check advisories from the major airlines -- American Airlines, Delta, United, US Airways, AirTran, JetBlue, and Southwest -- on their websites.
Middle Eastern, European and Asian airlines also grounded flights in and out of the United States' Eastern Seaboard as Sandy approached.
The good news is that the storm is happening during a slow travel season and airlines canceled many of the flights in advance, minimizing the number of stranded passengers, Farecompare.com Chief Executive Rick Seaney said Monday.
"Barring significant airport damage, flight patterns should be back to normal by the end of the weekend," Seaney said.