WASHINGTON — Airlines cancelled hundreds of flights as Tropical Storm Isaac lashed southeastern Florida Sunday, with service not expected to resume fully until late Monday.

The airports in Miami and Fort Lauderdale were hit the hardest, cancelling 589 flights – the vast majority of the 742 U.S. flights grounded overall because of the storm as of Sunday afternoon, according to the flight-tracking service FlightAware.

American Airlines and its American Eagle affiliate cancelled 486 flights. The last American flight left Miami at noon Sunday. The airline expects to be fully operational out of Miami by noon Eastern time on Monday, said airline spokesman Matt Miller. American runs a hub in Miami, a jumping-off point for flights to the Caribbean and Latin America.

Overall, airlines have cancelled 184 flights for Monday but expect to be operating normally by late Monday, according to FlightAware.

Isaac, already carrying winds of more than 60 miles an hour, was expected to cross the Keys by late afternoon. The storm will likely pick up strength from the warm, open waters of the Gulf of Mexico and strike as a dangerous Category 2 hurricane somewhere between New Orleans and the Florida Panhandle on Wednesday, the seventh anniversary of Hurricane Katrina.

Louisiana Governor Bobby Jindal declared a state of emergency ahead of Isaac late Sunday and urged voluntary evacuations for coastal parishes in the state.

Inside the American Airlines terminal in Miami, travelers craned for a look out of one of the doors as Isaac pelted the airport with strong rain and wind.

At Fort Lauderdale-Hollywood International Airport, the check-in line at the Southwest Airlines counter was completely empty at 7 a.m. Typically at that time on a Sunday the area is jammed, mainly by people leaving from vacations and cruises.

Delta Air Lines dropped three round-trip flights between its Atlanta hub and hard-hit Key West. "No others as of yet," Delta spokesman Morgan Durrant said by email Sunday afternoon. "We anticipate running a full schedule with the exception of Key West."

United Airlines and its United Express affiliate dropped 26 flights in the path of the storm.

Tampa, where the Republican party postponed the start of its political convention because of bad weather, has largely been spared flight cancellations: Just 26 inbound and outbound Tampa flights had been cancelled Sunday and four Monday, according to FlightAware.

The airlines are waiving fees for travelers who have to change their plans because of Isaac.

Amtrak on Saturday suspended part of its Silver Service line between Miami and Orlando through Monday "as a precaution against potential damaging winds and flooding."

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Associated Press writer Tim Reynolds in Miami contributed to this report.

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  • Heather Boss, right, and Brittney Lambert, both of Oklahoma, have fun in a flooded street due to heavy rains in Key West, Fla., Sunday, Aug. 26, 2012 as heavy storm winds and rain hit the northern coast. Rain bands from Tropical Storm Isaac are expected to continue streaming across Marion County Monday as the ninth named storm of the 2012 hurricane season continues toward the northern Gulf of Mexico. National Weather Service officials in Jacksonville on Sunday said Marion County began getting rain bands from Isaac around 2 p.m. and that the rain would continue through Tuesday. (AP Photo/Alan Diaz)

  • Victoria Balladares and boyfriend Jose Requejo experience the rain at Miami Beach as Tropical Storm Isaac hits the area on Sunday, Aug., 26, 2012, in Miami. Isaac gained fresh muscle Sunday as it bore down on the Florida Keys, with forecasters warning it could grow into a dangerous Category 2 hurricane as it nears the northern Gulf Coast. (AP Photo/The Miami Herald, Carl Juste)

  • Anton Snitgen, Jenna Curl, Jackie Curl and Michael Manemut run along a dock at Key West Bight Marina in Key West, Fla., as Tropical Storm Isaac hits the area on Sunday, Aug., 26, 2012. Isaac gained fresh muscle Sunday as it bore down on the Florida Keys, with forecasters warning it could grow into a dangerous Category 2 hurricane as it nears the northern Gulf Coast. (AP Photo/The Miami Herald, Walter Michot)

  • A man walks on the beach in Key West, Fla., Sunday, Aug. 26, 2012 as heavy winds hit the northern coast from Tropical Storm Isaac. Isaac is expected to continue streaming across Marion County Monday as it continues toward the northern Gulf of Mexico. National Weather Service officials in Jacksonville on Sunday said Marion County began getting rain bands from Isaac around 2 p.m. and that the rain would continue through Tuesday. (AP Photo/Alan Diaz)

  • A person braves the rain at Clarence Higgs Beach in Key West, Fla., as Tropical Storm Isaac hits the area on Sunday, Aug. 26, 2012. Isaac gained fresh muscle Sunday as it bore down on the Florida Keys, with forecasters warning it could grow into a dangerous Category 2 hurricane as it nears the northern Gulf Coast. (AP Photo/The Miami Herald, Walter Michot)

  • Folko Weltzien, 38, kite surfs as high winds from Hurricane Isaac gusts on Sunday, Aug. 26, 2012, in Miami. Isaac gained fresh muscle Sunday as it bore down on the Florida Keys, with forecasters warning it could grow into a dangerous Category 2 hurricane as it nears the northern Gulf Coast. (AP Photo/The Miami Herald, Carl Juste)

  • Heavy storm clouds hover over the skyline of downtown Miami as Tropical Storm Isaac's weather bands reach the Miami area aon Sunday, Aug. 26, 2012. Isaac gained fresh muscle Sunday as it bore down on the Florida Keys, with forecasters warning it could grow into a dangerous Category 2 hurricane as it nears the northern Gulf Coast. (AP Photo/The Miami Herald, Carl Juste)

  • Trees down in Midtown Miami.

  • A cyclist rides his bike in Key West, Fla., Sunday, Aug. 26, 2012. Tropical Storm Isaac gained fresh muscle Sunday as it bore down on the Florida Keys, with forecasters warning it could grow into a dangerous Category 2 hurricane as it nears the northern Gulf Coast. (AP Photo/Alan Diaz)

  • A person walks by a sign warning about Hurricane Isaac, in Key West, Fla., Sunday, Aug. 26, 2012. Isaac gained fresh muscle Sunday as it bore down on the Florida Keys, with forecasters warning it could grow into a dangerous Category 2 hurricane as it nears the northern Gulf Coast. (Alan Diaz)

  • Shira Edllan Gervasi, of Israel, puts her name on plywood protecting a storefront in Key West, Fla., in anticipation of Tropical Storm Isaac on Saturday, Aug. 25, 2012. Isaac's winds are expected to be felt in the Florida Keys by sunrise Sunday morning. (AP Photo/Alan Diaz)

  • Isaac Bears Down On Florida Keys

    MARATHON, FL - AUGUST 26: A man rides his bike along Overseas Highway as Tropical Storm Isaac begins to move toward the Florida Keys on August 26, 2012 in Islamorada, Florida. According to reports, Isaac has become stronger as it moves toward the Florida Keys and forecasters say it could strengthen into a Category 2 storm. (Photo by Marc Serota/Getty Images)

  • Isaac Bears Down On Florida Keys

    MARATHON, FL - AUGUST 26: People ride bikes as as Tropical Storm Isaac begins to move ashore on August 26, 2012 in Marathon, Florida. According to reports, Isaac has become stronger as it moves toward the Florida Keys and forecasters say it could strengthen into a Category 2 storm. (Photo by Marc Serota/Getty Images)

  • Florida Keys Under Hurricane Warning As Isaac Tracks North

    KEY WEST, FL - AUGUST 25: Arthur Asti installs storm shutters on August 25, 2012 in Key West, Florida. Residents in the Florida Keys are preparing after a Hurricane Warning was issued as Tropical Storm Isaac tracks north. (Photo by Marc Serota/Getty Images)

  • Florida Keys Under Hurricane Warning As Isaac Tracks North

    KEY WEST, FL - AUGUST 25: Two girls enter a K-Mart store on August 25, 2012 in Key West, Florida. Residents in the Florida Keys are preparing after a Hurricane Warning was issued as Tropical Storm Isaac tracks north. (Photo by Marc Serota/Getty Images)

  • Craig Jones, left, and Kimberly Branson secure their boat in Key West, Fla., Sunday, Aug. 26, 2012 in preparation for Tropical Storm Isaac. Tropical Storm Isaac gained fresh muscle Sunday as it bore down on the Florida Keys, with forecasters warning it could grow into a dangerous Category 2 hurricane as it nears the northern Gulf Coast. (Alan Diaz)

  • The southernmost point marker is covered in plastic sheeting in Key West, Fla., Saturday, Aug. 25, 2012, in preparation for Tropical Storm Isaac, Saturday, Aug. 25, 2012. Isaac's winds are expected to be felt in the Florida Keys by sunrise Sunday morning. (AP Photo/Alan Diaz)

  • Richie Moretti, left, and Bette Zirkelback release a kemps ridley turtle into an indoor tank in Marathon, Fla., Saturday, Aug. 25, 2012 . The turtles were moved from outside tanks to safer indoor tanks for protection in anticipation of Tropical Storm Isaac, Saturday, Aug. 25, 2012. Isaac's winds are expected to be felt in the Florida Keys by sunrise Sunday morning. (Alan Diaz)

  • Dale Shelton waits to be taken to a shelter in Key West, Fla., Saturday, Aug. 25, 2012, as he prepares for the arrival of Tropical Storm Isaac, Saturday, Aug. 25, 2012. Isaac's winds are expected to be felt in the Florida Keys by sunrise Sunday morning. (AP Photo/Alan Diaz)

  • A houseboat is towed in the middle keys as the Florida Keys prepare for Tropical Storm Isaac, Saturday, Aug 25, 2012. Florida Gov. Rick Scott had declared a state of emergency and a hurricane warning has been issued for the Florida Keys, as officials warn tourists to leave. (AP Photo/The Miami Herald, Walter Michot)

  • Florida Keys Under Hurricane Warning As Isaac Tracks North

    KEY WEST, FL - AUGUST 25: Cars leave the Lower Keys on August 25, 2012 in Key West, Florida. Residents in the Florida Keys are preparing after a Hurricane Warning was issued as Tropical Storm Isaac tracks north. (Photo by Marc Serota/Getty Images)

  • Vehicles wait in line for gasoline at the Sam

  • Harley Rojas dismantles the tarp next to his mobile home at the Sunshine Key RV Resort as the Florida Keys prepare for Tropical Storm Isaac, Saturday, Aug 25, 2012. Florida Gov. Rick Scott had declared a state of emergency and a hurricane warning has been issued for the Florida Keys, as officials warn tourists to leave. (AP Photo/The Miami Herald, Walter Michot)

  • Kerol Obando and her son Andres exit a Publix grocery store in Tavernier, Fla., as the Florida Keys prepare for Tropical Storm Isaac, Saturday, Aug 25, 2012. Florida Gov. Rick Scott had declared a state of emergency and a hurricane warning has been issued for the Florida Keys, as officials warn tourists to leave. (AP Photo/The Miami Herald, Walter Michot)

  • Florida Keys Under Hurricane Warning As Isaac Tracks North

    MARATHON, FL - AUGUST 25: A man windsurfs on August 25, 2012 in Marathon, Florida. Residents in the Florida Keys are preparing after a Hurricane Warning was issued as Tropical Storm Isaac tracks north. (Photo by Marc Serota/Getty Images)

  • Florida Keys Under Hurricane Warning As Isaac Tracks North

    KEY WEST, FL - AUGUST 25: A sign is posted on the wall of a bar on Duval Street on August 25, 2012 in Key West, Florida. Residents in the Florida Keys are preparing after a Hurricane Warning was issued as Tropical Storm Isaac tracks north. (Photo by Marc Serota/Getty Images)

  • Florida Keys Under Hurricane Warning As Isaac Tracks North

    KEY WEST, FL - AUGUST 25: Cars leave the Lower Keys on August 25, 2012 in Key West, Florida. Residents in the Florida Keys are preparing after a Hurricane Warning was issued as Tropical Storm Isaac tracks north. (Photo by Marc Serota/Getty Images)

  • Connie Rivero and her son Anthony Amador fill plastic bags with sand at the Hollywood Public Works Department as they prepare for possible floods from Tropical Storm Isaac on Saturday, Aug. 25, 2012, in Hollywood, Fla. Isaac was expected to pass over the Florida Keys as a hurricane late Sunday or early Monday. (AP Photo/The Miami Herald, Al Diaz) MAGS OUT

  • Most of the bottled water at Wal-Mart in Fort Walton Beach, Fla. was purchased by noon on Saturday August 25, 2012 in preparation for Tropical Storm Isaac which is forecasted to make landfall in the Florida Panhandle as a hurricane on Tuesday. (AP Photo/Northwest Florida Daily News, Nick Tomecek)

  • Lowes employees, Robert Tucker, right, and John Lucenti, left, load plywood for Terry King, back, and Ofelia Murphy at Lowes in Fort Walton Beach, Fla., Saturday August 25, 2012. Murphy said they needed some plywood to cover their windows in preparation for Tropical Storm Isaac which is forecasted to make landfall in the Florida Panhandle as a hurricane on Tuesday. (AP Photo/Northwest Florida Daily News, Nick Tomecek)

  • Florida Keys Under Hurricane Warning As Isaac Tracks North

    KEY WEST, FL - AUGUST 25: Tourists take in the sites on August 25, 2012 in Key West, Florida. Residents in the Florida Keys are preparing after a Hurricane Warning was issued as Tropical Storm Isaac tracks north. (Photo by Marc Serota/Getty Images)

  • Florida Keys Under Hurricane Warning As Isaac Tracks North

    KEY WEST, FL - AUGUST 25: A woman walks thru Malory Square on August 25, 2012 in Key West, Florida. Residents in the Florida Keys are preparing after a Hurricane Warning was issued as Tropical Storm Isaac tracks north. (Photo by Marc Serota/Getty Images)

  • Yoni Haim, left, and Jessica Yeshalek board their storefront as they prepare for Tropical Storm Isaac, Saturday, Aug. 25, 2012. Isaac's winds are expected to be felt in the Florida Keys by sunrise Sunday morning. (AP Photo/Alan Diaz)

  • Florida Keys Under Hurricane Warning As Isaac Tracks North

    ISLAMORADA, FL - AUGUST 25: A man secures his boat as the Florida Keys are under a Hurricane Warning as Tropical Storm Isaac tracks North on August 25, 2012 in Islamorada, Florida. (Photo by Marc Serota/Getty Images)

  • Florida Keys Under Hurricane Warning As Isaac Tracks North

    MARATHON, FL - AUGUST 25: People enter a store whie the Florida Keys are under a Hurricane Warning as Tropical Storm Isaac tracks North on August 25, 2012 in Marathon, Florida. (Photo by Marc Serota/Getty Images)

  • Florida Keys Under Hurricane Warning As Isaac Tracks North

    KEY WEST, FL - AUGUST 25: A worker clears a power line on August 25, 2012 in Key West, Florida. Residents in the Florida Keys are preparing after a Hurricane Warning was issued as Tropical Storm Isaac tracks north. (Photo by Marc Serota/Getty Images)

  • Florida Keys Under Hurricane Warning As Isaac Tracks North

    MARATHON, FL - AUGUST 25: A man installs shutters over a restaurant while the Florida Keys are under a Hurricane Warning as Tropical Storm Isaac tracks Northwest on August 25, 2012 in Marathon, Florida. (Photo by Marc Serota/Getty Images)

  • Tampa Prepares For Republican National Convention And Potential Hurricane

    CLEARWATER, FL - AUGUST 25: Alex Guilbaud runs with a skimboard as storm clouds build offshore on August 25, 2012 in Clearwater, Florida. Tampa area residents wait for Tropical Storm Isaac as they prepare for the Repulican National Convention which will be held in Tampa during the week of August 27th. (Photo by Tom Pennington/Getty Images)

  • Tampa Prepares For Republican National Convention And Potential Hurricane

    TAMPA, FL - AUGUST 25: Lee Bittner buys a generator and a bottle of water at Home Depot on August 25, 2012 in Tampa, Florida. Area residents are preparing for Tropical Storm Isaac just before the Repulican National Convention which will be held at the Tampa Bay Times Forum during the week of August 27th. The Tropical Storm might become a hurricane by the time it hits ground. (Photo by Joe Raedle/Getty Images)

  • Cheri Senecal walks with a bag of personal items to a shelter in Key West, Fla., Saturday, Aug. 25, 2012 as she prepares for Tropical Storm Isaac, Saturday, Aug. 25, 2012. Isaac's winds are expected to be felt in the Florida Keys by sunrise Sunday morning. (AP Photo/Alan Diaz)

  • Isaac Bears Down On Florida Keys

    MARATHON, FL - AUGUST 26: A man tends to his boat as Tropical Storm Isaac begins to move toward the Florida Keys on August 26, 2012 in Islamorada, Florida. According to reports, Isaac has become stronger as it moves toward the Florida Keys and forecasters say it could strengthen into a Category 2 storm. (Photo by Marc Serota/Getty Images)

  • Florida Keys Under Hurricane Warning As Isaac Tracks North

    KEY WEST, FL - AUGUST 25: Two men install storm shutters on Duval Street on August 25, 2012 in Key West, Florida. Residents in the Florida Keys are preparing after a Hurricane Warning was issued as Tropical Storm Isaac tracks north. (Photo by Marc Serota/Getty Images)

  • A message warns drivers of severe weather on Sunday, Aug. 26, 2012, in Miami. Isaac gained fresh muscle Sunday as it bore down on the Florida Keys, with forecasters warning it could grow into a dangerous Category 2 hurricane as it nears the northern Gulf Coast. (AP Photo/The Miami Herald, Hector Gabino)

  • In this photo provided by Florida Power & Light Company, line specialist Dustin Pezet works to restore power as Tropical Storm Isaac strikes in Miami on Sunday, Aug. 26, 2012. Isaac gained fresh muscle Sunday as it bore down on the Florida Keys, with forecasters warning it could grow into a dangerous Category 2 hurricane as it nears the northern Gulf Coast. (AP Photo/Florida Power & Light Company, David Adame)

  • Tampa Prepares For Republican National Convention And Potential Hurricane

    TAMPA, FL - AUGUST 26: Republican Rachel Bolch Thach walks along a rainy beach on August 26, 2012 in Tampa, Florida. Tampa is preparing for the start of the Republican National Convention at the Tampa Bay Times Forum. The RNC is scheduled to convene on August 27 and will hold its first session on August 28 as Tropical Storm Isaac threatens disruptions due to its proximity to the Florida peninsula. (Photo by Spencer Platt/Getty Images)

  • Isaac Bears Down On Florida Keys

    MARATHON, FL - AUGUST 26: People stand near downed branches as Tropical Storm Isaac begins to move ashore on August 26, 2012 in Marathon, Florida. According to reports, Isaac has become stronger as it moves toward the Florida Keys and forecasters say it could strengthen into a Category 2 storm. (Photo by Marc Serota/Getty Images)