The unprecedented freak storm is expected to bring sheets of rain, high winds and even heavy snow. The latest numbers - 707 flights have been canceled on Sunday alone. Newark Liberty International Airport is the most affected with over 265 cancellations on Sunday. That airport is a United Airlines hub. For Monday, 3,700 flights have been canceled with Newark most impacted again with 774 cancellations.
Dulles International Airport and Philadelphia International Airport are also seeing hundreds of cancellations. Delta Air Lines announced on their Twitter account that all of their flights in and out of New York City and Philadelphia airports on Monday have been canceled.
Most air traffic control towers shut down when winds reach 60-70 knots. The main factor that will result in early flight disruptions is mass transit shutdowns and the availability of airline and airport staff due to their need to prepare for the hurricane. For example, New York City's transit service will suspend bus, subway and commuter rail service Sunday night.
Also, a big factor potentially affecting the reopening coastal airports is high tide. LaGuardia Airport is the biggest airport to be affected, followed by JFK International Airport.
U.S. Airways is expected to be the most affected because the airline's hubs are near New York and Washington, D.C. United is shutting down D.C. operations Sunday night with plans to resume flights sometime Tuesday afternoon. The airline will also shut down Philadelphia, JFK, Newark and LaGuardia operations Sunday night with plans to resume Tuesday night.
The number of flight cancellations Monday and Tuesday is expected to rise as Hurricane Sandy nears landfall.
Most carriers are allowing travelers to reschedule without charging fees.
The New York Stock Exchange and other U.S. financial markets are shutting down Monday The operator of the NYSE announced the decision late Sunday along with exchange operators Nasdaq OMX Group and CME Group. They said markets might be closed Tuesday "pending confirmation."
The exchange operators said they made the call after consulting with each other, regulators and government officials. They cited concerns about the market's ability to function without disruption and the safety of people who work there.
The Associated Press contributed to this report.