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 come back online.
Most city and commuter transit remained nearly at a standstill on Tuesday, while some area airports are expecting to start offering service on Wednesday. Other Northeast and mid-Atlantic airport and ground transportation systems were slowly coming back to life.
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 will 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. Newark Liberty International Airport is also expected to be closed through Wednesday as engineers assess storm damage, Port Authority spokesman Anthony Hayes said Tuesday afternoon.
Hayes 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.
Thousands of flights canceled
More than 18,100 flight have been canceled as a result of the storm, according to flight tracking site FlightAware.com.
More than 8,000 Tuesday flights were canceled as of 4 p.m., FlightAware figures show. LaGuardia and Newark led the way with 1,200 cancellations each.
On Tuesday morning, airlines had already canceled 1,875 flights for Wednesday. More cancellations are expected as airport staffs assess damage and airlines reconfigure their flight schedules.
More signs of optimism
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 (and 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.
Public transportation upheaval
New York City's critical massive public transit network was still 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. Lhota said in an online statement.
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.
By noon Tuesday, five of the transportation authority's seven bridges were reopened. Bus service was expected to have a full schedule on Wednesday. The MTA said it's too early to estimate how long restoring systemwide service will take.
In New Jersey, all NJ Transit services remain suspended until further notice, with the exception of limited service in Camden. Commuter bus and train service will be running Wednesday in Maryland, according to the Maryland Transit Administration.
Some service in Philadelphia was restored at noon on Tuesday, and Southeastern Pennsylvania's regional rail commuter lines are 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.
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 are still operating, but they are stopping short of the storm-affected states. Consult Amtrak's website for more details.