More than 14,000 flights have been cancelled and many more cancellations are expected to wreak havoc on travel plans as airports slow operations and airlines scrap flights because of Hurricane Sandy.  

Passengers are stranded across the globe, from Los Angeles to as far as Hong Kong, as carriers cancel flights in and out of New York City, the nation’s busiest airspace.

Some airspace activity is expected to slowly resume on Tuesday, but with Sandy bringing winds of up to 90 miles per hour and storm surges higher than 11 feet, the Port Authority continues to warn travelers of potential delays and shutdowns.

John F. Kennedy International Airport and LaGuardia Airport, both based in New York, were facing “significant disruption to operations” Monday, with LaGuardia completely closing as of 8 p.m. ET.

In New Jersey, Newark Liberty International Airport’s delay index was set at “high,” representing “severely impacted departure conditions,” including many cancellations and delays. The airport remained open last night but planes were grounded.

Washington D.C.’s Dulles International Airport and Reagan National Airport remain open but airlines have cancelled flights. The Metropolitan Washington Airports Authority is encouraging fliers to contact carriers directly to rebook trips.

At Philadelphia International Airport, all operations have been suspended until further notice.

“Travelers should consult with their airlines for the status of flights before coming to the airport,” the Port Authority of New York and New Jersey said in an alert.

Nearly 14,000 flights were cancelled as of Monday evening, according to FlightAware, and the number continued to grow overnight.

United Continental (UAL), Delta (DAL) and American Airlines led the flight cancellations, followed by US Airways (LCC), Southwest (LUV) and JetBlue (JBLU), and a slew of other regional and international airlines like AirTran, Pinnacle Airlines, Air Canada, British Airways, Alaska Airlines (ALK), Virgin America and China Airlines.

Delta, which cancelled more than 2,500 flights as of Monday, said it is aiming to resume limited flights at JFK and LaGuardia on Tuesday with a full restart targeted for Wednesday. Flying at other U.S. East Coast airports is expected to resume by mid-morning on Tuesday.

United has agreed to waive cancellation and rescheduling fees for customers ticketed on flights to, from or through impacted cities from Oct. 28 through Oct. 31.

Two days before Halloween, the “Frankenstorm” has travel plans in disarray.

Guy Nestor, a meteorologist with Mobile Weather Team who was on site at the CIMB Classic golf tournament in Malaysia for the last week, was stuck in Doha, Qatar, on a layover after his connecting flight through Dulles was cancelled on Monday. Nestor secured a transfer in Houston for Tuesday on his quest to reach his family in Pittsburgh.

Mike McCann, an employee at Enterprise Rent-A-Car, is stuck in Miami where he was vacationing after his flight to LaGuardia Sunday night was cancelled. Flying on American Airlines, he tried to squeeze onto an earlier flight but was told planes were grounded or completely full until Thursday.

“Today and tomorrow everything is cancelled. Wednesday is tentatively cancelled,” McCann said.

John Kingston, Director of News at Platts, a news service specializing in the energy sector, is capping off an unfortunate few days that began when the Detroit Tigers lost game three in the World Series Saturday night.

The Tigers fan flew out to Detroit on Sunday morning to catch game 4 with plans to fly back to New York on Tuesday morning. After an ugly sweep by the San Francisco Giants, Kingston learned his American Airlines flight was postponed a day to Wednesday.

“Fingers are crossed,” Kingston said.

Since driving a rental car home to New York would have run him at extra $500, he chose to bunker down at a hotel near Detroit Metro Airport and await a resumption in East Coast airspace activity. 

“I have plenty of work to do and given that I’m sure my house will eventually lose power, I am probably going to be more productive here,” Kingston said. “But let’s face it: airport hotels are hardly examples of warm, beautiful places to stay.”

On Sunday night, the Port Authority closed NYC’s massive public transit system. The Holland Tunnel that connects Manhattan and New Jersey, George Washington Bridge and other bridges and tunnels into Manhattan were closed on Monday.

The two-day airspace standstill is expected to cost both the global business and leisure travel industries hundreds of millions of dollars.

“For the most part we’re seeing a fairly widespread to almost complete shutdown of business travel activity from Virginia up the coast to New England,” said Joe Bates, vice president of research at the Global Business Travel Association.

Depending on how quickly the storm moves through, how many people are out of power and the extent of damages, travel could be stunted or at least face “lingering impacts” through the end of the week, Bates said.

Some travel spend will be made up as plans are rescheduled, but Bates said a “large chunk” will be completely lost.

Follow Jennifer Booton on Twitter at @Jbooton