NEW YORK — The 26 miles might be the easy part.

The biggest challenge for this New York City Marathon on Sunday could be getting to the start, not the finish.

The mayor of storm-battered New York says the race is still on, but flying in runners from out of town will be tricky, and there may not be a subway to get everyone to the starting line.

Superstorm Sandy shut down transportation, closed airports, flooded streets and left scores of neighborhoods without power — formidable obstacles for the organizers.

Still, they were moving forward with plans Tuesday, leaving open the possibility of changes from past years.

"The marathon has always been a special day for New Yorkers as a symbol of the vitality and resiliency of this city," New York Road Runners President Mary Wittenberg said in a statement.

The 26.2-mile route through the five boroughs mostly avoids the areas hit hardest by flooding. Organizers were expecting nearly 50,000 runners before the storm hit. However they have no idea how many will actually make it to start the race.

"We will keep all options open with regard to making any accommodations and adjustments necessary to race day and race weekend events," she said.

Mayor Michael Bloomberg said it could be four or five days before the subways were running again, which means they may not be available on race day. Commuter trains may not be operating normally, either.

The starting line is on Staten Island and about half the entrants normally would take the ferry and others would take buses through the Brooklyn-Battery Tunnel. Both were closed because of flooding.

The marathon was projected to pour $340 million into the city, but it also requires major support from municipal departments strained by the monster storm that wreaked havoc Monday evening.

"The city is rightfully focused on assessment, restoration and recovery," Wittenberg said.

JFK and Newark airports were set to reopen Wednesday and LaGuardia remains closed.

Nearly 20,000 amateur international runners were scheduled to fly in for the race. Family and friends of runners must somehow find a way to their viewing spots.

Runners who can't get to New York should have until Saturday instead of Wednesday to withdraw from the race and reserve a spot in the 2013 marathon, but they won't get a refund and will have to pay again next year.

Race organizers expected to reschedule the elite runners' flights to get them in on time. The 43rd edition of the marathon is set to include three Olympic medalists and the reigning women's world champion.

Kenya's Wilson Kipsang won bronze in the Olympic men's marathon. His challengers include 2011 Chicago Marathon champ Moses Mosop of Kenya, 2010 New York winner Gebre Gebremariam of Ethiopia and top American Meb Keflezighi.

In 2009, Keflezighi became the first American since Alberto Salazar in 1982 to win New York. He was fourth at the Olympics.

Ethiopia's Tiki Gelana won gold and Russia's Tatyana Arkhipova took bronze in the women's race in London. Edna Kiplagat of Kenya won a world title a year earlier.

Last year's runner-up in New York, Ethiopian Buzunesh Deba, doesn't have to get on a plane to make the race. She knows exactly what the city is going through — Deba lives in the Bronx.