New York (CNN) -- While Superstorm Sandy's punch has weakened, its wrath is still being felt.
Walloped by severe storm damage and flooding, the New York City area's extensive transportation system is struggling to get back online, while some area airports are resuming service on Wednesday. Other Northeast and mid-Atlantic airport and ground transportation systems were gradually resuming operations.
Here's what's happening in many of the affected areas:
Airline operations resuming
New York City's John F. Kennedy International Airport and Newark Liberty International Airport in New Jersey would open Wednesday morning for limited service, the Port Authority of New York and New Jersey announced Tuesday night. In preparation for JFK's opening, some airlines were to land aircraft at the airport late Tuesday night.
New York City's LaGuardia International Airport is expected to remain closed through Wednesday because of significant damage.
The Port Authority strongly advised travelers to contact their airlines before heading to any of the airports, even if they are open.
Delta Air Lines expects to resume limited domestic service to JFK International Wednesday afternoon.
Some of the Northeast's other airports are coming back to life. The Boston and Philadelphia airports and the three airports serving the Washington/Baltimore area are open and operational with some airlines already resuming limited flight service.
Southwest Airlines (including subsidiary AirTran Airways) is planning to resume normal operations by midday Wednesday across most of the Northeast and mid-Atlantic regions, with the exception of the New York City area and Philadelphia airports, according to a statement. 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.
More than 19,500 flights have been canceled as a result of the storm, according to flight tracking site FlightAware.com.
More than 7,000 Tuesday flights were canceled, FlightAware figures show. By 9 a.m. Wednesday, more than 2,800 Wednesday flights and more than 480 Thursday flights had been canceled.
Public transportation upheaval
New York City's critical public transit network was still crippled Wednesday, although bus service was operating "as close to a normal weekday schedule as possible," according to the Metropolitan Transportation Authority's website.
The MTA's commuter railroad service remained suspended Wednesday.
Seven subway tunnels under the East River flooded in the course of the storm, and two Long Island Rail Road tubes and two vehicular tunnels were inundated. One subway bridge, three subway yards and six bus facilities also were flooded, according to MTA's website.
Six of MTA's seven bridges were open Wednesday, the exception being the Cross Bay Bridge. The MTA said it's too early to estimate how long it will take to restore systemwide service.
In New Jersey, most NJ Transit services remained suspended Wednesday, with the exception of bus service in Camden County operating on a weekday schedule. Commuter bus and train service will be running Wednesday in Maryland, according to the Maryland Transit Administration.
Some service in Philadelphia was restored Tuesday, and Southeastern Pennsylvania's regional rail commuter lines were scheduled to resume service Wednesday morning, according to a SEPTA statement.
In Boston, most transit service resumed Tuesday, with some delays, according to the Massachusetts Bay Transportation Authority.
In Washington, bus and rail service was restored on modified schedules. Normal operations were expected to resume Wednesday.
Amtrak will provide some modified service between Newark, New Jersey, and points south starting Wednesday. Trains between Harrisburg, Pennsylvania, and Philadelphia, and between Boston and Portland, Maine, will also run.
However, trains directly to and from Penn Station in New York will be idle. Consult Amtrak's website for more details.
CNN's Joshua Levs, Aaron Smith and Greg Botelho contributed to this report.