Whether by plane, car or train, hundreds of thousands of people scrambled to get out of South Florida on Wednesday ahead of Hurricane Irma, a massive system forecasters say is the most powerful storm to hit the Atlantic Coast in more than a decade.

The storm, with maximum sustained winds near 185 mph, moved over the Leeward Islands Wednesday morning before moving to the northern Virgin Islands and Puerto Rico.

Forecasters say it will reach South Florida sometime between Friday night and Monday.

[Evacuations underway in Florida as Hurricane Irma menaces the Caribbean]

To accommodate surging demand of people trying to flee, airlines including American and Delta added flights or brought in larger planes and waived change fees for passengers who need to cancel or rebook their flights.

Even so, hundreds of flights were canceled Wednesday, and airlines strongly advised passengers to check before leaving for the airport.

Late Wednesday, American Airlines announced it would begin winding down its operations in Florida and had canceled flights at its Miami hub as well as to airports in Fort Lauderdale, Fort Myers, Sarasota and West Palm Beach. In addition, it canceled a handful of international flights from Europe and South American that were scheduled to land in Miami on Friday.

Many of those leaving Wednesday said they didn't want to gamble on getting stranded.

Janet and Tom Wrabel of Fairfield, Conn., had been visiting their daughter in Fort Lauderdale when they saw the storm brewing and decided to cut their vacation a couple of days short. Neither was crushed, though this clearly was suboptimal.

"We would rather be here reclining by a pool right now instead of getting on a plane," said Tom, 62, as the couple prepared to leave.

Officials at Key West International Airport said they would suspend commercial operations at the end of the day Thursday, and Miami International Airport advised travelers it will halt operations at the airport when winds reach 55 mph. Generally, airlines do not operate in sustained crosswinds that exceed 35 mph, and the Federal Aviation Administration tower ceases operations after winds of 55 mph, the airport noted.

On the state's roadways, long lines of cars and trucks could be seen traveling north on the Florida Turnpike as tourists and residents fled the Florida Keys — among the first areas to be under a mandatory evacuation order. Gas stations were also jammed as Floridians rushed to fill their tanks before Irma's arrival. Grocery stores reported running out of bottled water.

Airlines, still reeling from Harvey, which swept through Texas last month, were preparing for another hit.

Both American and Southwest airlines have a significant presence in Florida and the Caribbean. American has a hub at Miami International, and Southwest has a large operation at Fort Lauderdale's airport.

The travel picture is expected to worsen as Irma moves closer to Florida.

There were anecdotal reports from travelers that airlines were charging exorbitant fares for flights out of areas in the path of the storm, but airlines denied that was the case.

Even so, Paul Hudson, president of the consumer rights advocate Flyers Rights, said the group was checking into reports of fares of up to $1,000 to get out of the Miami area, where depending on the destination, a one-way ticket can typically go for as little as $99.

Leigh Dow, a public relations executive from Arizona, used her twitter account to chide Delta Air Lines for raising the price of a ticket from Miami to Phoenix's Sky Harbor Airport from $547 to $3,200.

Dow's tweet was retweeted more than 23,000 times.

She later tweeted Delta officials contacted her and the situation had been resolved.

[Latest models show increasing threat to George and the Carolinas]

Trebor Banstetter, a spokesman for Delta, said Dow was apparently reacting to information from the travel website Expedia, but when she contacted the airline directly, he said, "She got a price she was happy with."

"We have not increased prices in response to the hurricane," Banstetter said.

Similarly, JetBlue was offering travelers trying to get out of Irma's path remaining seats at reduced fares ranging from $99 to $159.

The main worry remained the storm's impact on South Florida, home to 6 million people. President Trump on Tuesday declared an emergency in the state as well as the U.S. Virgin Islands and Puerto Rico. Florida Gov. Rick Scott (R) has ordered all 7,000 members of the Florida National Guard to report for duty Friday.

Evacuations began Wednesday morning in the Florida Keys, and state transportation officials were "aggressively clearing evacuation routes," officials said.

The main routes out of South Florida are Interstate 95 and the Florida Turnpike, which can be prone to gridlock on the best of days. In an effort to ease congestion, the governor ordered that no tolls be collected.

State officials say more mandatory evacuations would be ordered as the storm nears, and some urged residents to evacuate the area early and expect clogged roadways.

"Do not sit and wait for this storm to come," Scott said in a tweet. "Remember, we can rebuild your home — not your life."

Airport officials also urged caution, telling people to check with their airlines before venturing out and urging people not to use the airport as a shelter.

Meantime, residents who were leaving were keeping those staying behind in their thoughts.

Betsy Weidenmuller, 71, had booked a flight on Southwest out of Fort Lauderdale on Sunday at the urging of her son in New Orleans, who had told her, "I think this looks bad."

Weidenmuller said most of her neighbors are going to ride out the storm with friends or relatives who have generators. As she was heading to the airport, she got a text from a neighbor offering to hurricane-proof her home.

Weidenmuller was struck by the generosity. "It looks like keeping my neighbors supplied with scones has really paid off," she said with a smile.

Joel Achenbach contributed to this report from Florida.