MIAMI (REUTERS) - Airlines were racing against the clock to clear as many customers as possible from the likely Florida path of Hurricane Irma, as social and political pressure mounted for carriers to play a bigger role in aiding evacuations.

As the powerful storm threatened to rip through the Florida coast this weekend, airlines ramped up the number of flights available out of south Florida airports, where operations were likely to temporarily cease through the weekend and beyond.

But flights out of the area remained extremely limited. At Miami International Airport, many outbound flights were cancelled, leaving residents scrambling to rebook to anywhere outside the path of the storm.

American Airlines, which has one of the larger operations in south Florida, said on Thursday that it had added 16 flights out of Miami, amid more than 2,400 forced cancellations through Monday.

Delta Air Lines Inc said it had upsized aircraft and added flights to increase the number of available outgoing seats by 2,000. United Airlines added six flights out of Miami to its hubs, including Newark, New Jersey, and Chicago O'Hare.

All three carriers said they planned to mostly wind down south Florida operations by Friday evening.

An areas already pummelled by the powerful storm, flight operations had been rolled back and halted altogether.

A Delta-operated flight from New York to San Juan, Puerto Rico, and back, made headlines for narrowly avoiding the storm in a mission to evacuate another plane-full of passengers from the area ahead of Irma's landfall.

Flight-tracking website FlightRadar24.com saw the plane land for one last departure in the US territory located squarely in the path of Irma's landfall, fill with passengers, and make its successful flight back to New York on Wednesday. Other airlines had already ceased operations in the region.

PRICE-GOUGING

As residents sought to secure last-minute flights out of the dangerous Category 5 storm's path, airlines faced accusations of trying to capitalise on the panic and chaos by price gouging.

Under pressure from some members of Congress following social media reports, airlines have taken the unusual step of publicly announcing price caps on tickets out of areas in Irma's course.

Early on, carrier JetBlue capped flights out of the area at US$99 (S$134), and other carriers followed suit, capping fares at between US$99 and US$399 a ticket.

But while airlines offered some cheap flights out of south Florida after complaints, passengers said that did little good if all the flights were fully booked or cancelled.

Medical student Eric Slabaugh said he was dismayed by ticket prices over US$2,000 when he started looking for flights earlier this week. He got a ticket to Detroit for US$700, he said,"because nobody wants to go there."

"Publix can't charge US$50 for a case of water without getting accused of price gouging, but airlines can charge 50 times the price of a normal ticket. I don't think that's fair," Slabaugh said.

Airlines' customer service practices have come under fire in recent months, and just last year, US carriers were cleared in a federal investigation regarding exorbitant fare mark-ups in the wake of a deadly Amtrak derailment that drove up demand for air travel on some routes.

Senator Bill Nelson, a Florida Democrat who had been pressuring airlines to aid in evacuating Florida residents, spoke with airline executives on Thursday and urged them to add more flight outs of Florida.

His office said Nelson is "pleased" airlines were doing everything they could to "help get impacted Floridians to safety."

The Federal Aviation Administration is holding twice daily phone calls with airlines to talk about airport conditions, but does not plan to close the Miami airport on Friday, officials said.

Airlines are still planning for airport closures, however, and said they expect their operations to be impacted in the region at least through the weekend.

Also affected by the storm, Carnival Cruise Lines, which has major operations out of Florida ports, said on Thursday it had cancelled four of its Caribbean cruises, though it still planned to operate several more under modified itineraries.