Transit systems yet to return to service

NEW: Amtrak has no estimate for when trains to and from Penn Station will be back up Some New York City area airports set to offer limited service Wednesday The New York City transit system sustains "devastating" damage More than 18,000 flights have been canceled, a flight tracking site says Have you been affected by Hurricane Sandy? If so, share your images and footage with CNN iReport, but please stay safe. 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 Aerial images from the U.S. Coast Guard show the coastline in Brigantine, New Jersey, on Tuesday, October 30. Sandy struck land near Atlantic City, New Jersey, around high tide Monday night. View photos of the recovery efforts in New York. Homes and other buildings in Brigantine were destroyed in Sandy's wake. New Jersey Gov. Chris Christie described the devastation in the state as "unthinkable." Brigantine saw extensive damage from high winds and flooding. Homes are flooded Tuesday in Tuckerton, New Jersey. President Barack Obama signed major disaster declarations for New Jersey and New York, clearing the way for federal aid. A resident walks down a street covered in beach sand due to flooding from Hurricane Sandy in Long Beach, New York on Tuesday. Firefighters work to extinguish flames in a home in the Breezy Point neighborhood of Queens on Tuesday. The massive fire broke out during the storm and destroyed at least 80 homes Ted Wondsel, owner of Ted's Fishing Station in Long Beach, assesses the damage to his business Tuesday. People wait outside a shelter at the Bergen County Technical Schools Teterboro Campus on Tuesday in Hasbrouck Heights, New Jersey. Utility workers from Delmarva Power replace a power pole that was damaged during Hurricane Sandy in Ocean City, Maryland, on Tuesday. Dale Kelly sits on a bench Tuesday on a flooded street in Ocean City, New Jersey, which was hit hard by Superstorm Sandy. Ted Wondsel, left, of Point Lookout works on part of a dock destroyed in the storm in Long Beach on Tuesday. West Broadway in Long Beach is covered in beach sand due to flooding from Hurricane Sandy on Tuesday. Residents walk along a street covered in beach sand after floodwaters from Superstorm Sandy retreated Tuesday in Long Beach. A small plane damaged in the storm sits on a runway in Farmingdale, New York, on Tuesday. Streets remain flooded in portions of Ocean City, New Jersey. Utility workers repair a traffic signal damaged by the storm in Ocean City, New Jersey, on Tuesday. A Virgin Mary statue stands in the Breezy Point neighborhood of Queens, New York, on Tuesday after a fire fed by high winds destroyed at least 80 homes, officials said. President Barack Obama outlines the federal government's response to Superstorm Sandy at the Red Cross headquarters in Washington. Firefighters work to contain the fire in Queens on Tuesday. Some 200 firefighters battled the six-alarm blaze. A man surveys damage to sailboats Tuesday at a marina on City Island in New York. "My message to the federal government: no bureaucracy, no red tape, get resources where they're needed as fast as possible, as hard as possible, and for the duration," Obama said in Washington Tuesday. Both Obama and Republican presidential candidate Mitt Romney canceled campaign events. People stand on a mound of construction dirt on Tuesday to view a section of the uptown boardwalk in Atlantic City, New Jersey, that was destroyed by flooding. A firefighter looks through debris in Queens on Tuesday. In September, the same area endured severe weather as a powerful cold front brought heavy rain, high winds and a tornado. A malfunctioning generator billows black smoke at a building in New York on Tuesday. Mitt Romney helps gather donated goods for storm relief Tuesday in Kettering, Ohio. Emergency personnel help a resident of Little Ferry, New Jersey, onto a boat after rescuing her from floodwater on Tuesday. Dean Walter, left. and Henry Young walk along a seawall in Scituate, Massachusetts, with their surfboards after going into the heavy surf for about 20 minutes on Tuesday. Superstorm Sandy left New York's South Street Seaport flooded and covered in debris on Tuesday. Passers-by look at a car that was crushed by a tree near New York's financial district on Tuesday. Pedestrians and bikers cross the Brooklyn Bridge after the storm on Tuesday. People stand among the debris of the destroyed section of Atlantic City, New Jersey's, uptown boardwalk on Tuesday. Sailboats rest on the ground after being tipped over by Superstorm Sandy on City Island, New York, on Tuesday. Onlookers watch a dangling crane, damaged in the winds of Superstorm Sandy, atop a luxury high-rise under construction in midtown Manhattan on Tuesday. An onlooker snaps a photo of the damaged crane on Tuesday. Jolito Ortiz helps clean up a friend's apartment on New York's lower east side on Tuesday. A tidal surge created by Sandy flooded the Brooklyn Battery Tunnel in New York on Tuesday. A worker cuts down a tree near American University in Washington on Tuesday. A home badly damaged by Superstorm Sandy sits along the shoreline in Milford, Connecticut, on Tuesday. An emergency worker carries a resident through floodwaters in Little Ferry, New Jersey, on Tuesday. Police walk past debris left by the storm at Battery Park in New York on Tuesday. Floodwater splashes into the window of a building on the shore in Bellport, New York, on Tuesday. Rescue workers use a hovercraft to rescue a resident using a wheelchair from floodwaters in Little Ferry, New Jersey, on Tuesday. A resident of Little Ferry, New Jersey, assists in rescue efforts with his personal watercraft on Tuesday. The HMS Bounty, a 180-foot sailboat, is submerged in the Atlantic Ocean about 90 miles southeast of Hatteras, North Carolina, on Monday, October 29. A man walks through the debris of a 2,000-foot section of Atlantic City, New Jersey's "uptown" boardwalk on Tuesday. It was destroyed by flooding from Sandy. Downed trees are removed near the Korean War Veterans Memorial in Washington on Tuesday. Heavy surf buckles Ocean Avenue in Avalon, New Jersey, on Tuesday. Sam Rigby walks on Tuesday near an uprooted tree that grazed his house and hit his neighbor's house in Washington. A photographer shoots waves in Lake Michigan generated by the remnants of Sandy as they crash into the Chicago shoreline on Tuesday. A police officer helps remove a tree branch brought down during the storm in Washington on Tuesday. A man takes pictures of cars from the steps of a home on a flooded street at Hoboken in New Jersey, on Tuesday. A woman wades through water at the South Street Seaport in New York City on Tuesday. A street light and utility pole lie on the street in Avalon, New Jersey, on Tuesday. Atlantic City, New Jersey, resident Kim Johnson inspects the area around her flooded apartment building on Tuesday. A power line knocked over by a falling tree blocks a street in Chevy Chase, Maryland, on Tuesday. Workers shovel debris from the streets in Ocean City, Maryland, on Tuesday. A U.S. Coast Guard helicopter flies over Central Park in New York on Tuesday. A man jogs near a darkened Manhattan skyline on Tuesday after much of New York City lost electricity. Workers clear a tree blocking East 96th Street in Central Park in New York on Tuesday. View more photos of the recovery efforts in New York. 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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. In Washington D.C., bus and rail service was restored on modified schedules. Normal operations are expected to resume Wednesday. Amtrak will provide some modified service between Newark, New Jersey and places 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, and there is no estimate for when they might be back up. Consult Amtrak's website for more details. CNN's Joshua Levs, Aaron Smith and Greg Botelho contributed to this report.