FLORIDA (NYTIMES) - Passengers at an airport in Florida protested on Monday night (May 8) after the cancellation of multiple flights, leading to a confrontation with airline employees and sheriff's deputies who arrested three travellers while attempting to restore order.

According to the Broward County Sheriff's Office, the arrests were made after customers screamed at and threatened Spirit Airline employees, inciting unrest in a crowd of about 500 people at Fort Lauderdale-Hollywood International Airport.

Their anger was set off by the flight cancellations, the sheriff's office said in a statement, and deputies were sent in to calm the crowd.

Flight Aware, a flight-tracking site, indicated that 11 Spirit Airlines flights were cancelled at the airport on Monday (May 8) and that 30 were delayed.

Arrest reports assert that those detained were threatening to harm airline employees and challenging them to fights. All three of the people who were arrested were charged with disorderly conduct, inciting a riot and resisting arrest.

Video taken at the airport and posted to social media showed a scrum of passengers jostling with sheriff's deputies.

Paul Berry, a spokesman for the airline, said that Spirit was "shocked and saddened" by the violence and blamed the cancellations on airline pilots who he said were engaged in "unlawful labour activity" that was "designed to disrupt Spirit operations".

The airline filed a lawsuit in federal court on Monday (May 8) against the Air Line Pilots Association, International, which represents Spirit's pilots, accusing it of coordinating a "pervasive illegal work slowdown" that it said had led to the cancellation of about 300 Spirit flights since the beginning of May and had interfered with the travel plans of over 20,000 passengers.

The pilots' union disputed the airline's account, calling the lawsuit "unwarranted and counterproductive".

On Tuesday (May 9), however, a federal judge granted a temporary restraining order sought by the airline, instructing Spirit pilots and the union to refrain from activities aimed at disrupting normal operations, at least until a hearing scheduled for Monday (May 15).

"The court has spoken and Spirit pilots will fully comply with the order handed down, which is completely in line with our overriding goal: the resumption of normal operations," the union said in a statement. "We call on the company to join forces with ALPA and the Spirit pilots to do just that."

Senator Bill Nelson of Florida said from the floor of the US Senate on Tuesday (May 9) that he had spoken to the leaders of the airline and the union and encouraged them to "get this thing fixed and get it fixed quick".

The industry has seen periodic labour tension between pilots and carriers since the early part of the decade, as carriers began to recover from years of losses and pilots felt they weren't sharing in the gains.

"Pilots are very sensitive to executive compensation," said Mr Thomas Kochan, a professor at the Massachusetts Institute of Technology Sloan School of Management who follows the airline industry. "They consider themselves equal to executives in competence, intelligence, leadership, all those dimensions."

Pilots at some of the large legacy carriers, like Delta and United, have pressed for and received significant wage increases in recent years.

Spirit pilots, who tend to make less than their counterparts at the major carriers, went on strike for several days in 2010, citing low wages after several years of negotiations had failed to produce a contract.

More than 200 pilots for the cargo carrier ABX Air, whose customers include DHL and Amazon, briefly went on strike last fall before a federal judge ordered them back to work.

The pilots complained of chronic understaffing that was forcing them to work emergency shifts without adequate time off. Pilots at ABX and four other carriers who serve DHL continue to press for higher wages and benefits and better working conditions.

The Spirit lawsuit, which was filed in Florida's southern district, estimated that the airline had lost about US$8.5 million (S$12 million) in revenue because of its conflict with the association. The airline said that on Sunday (May 7) alone, it had to cancel 81 flights, representing 17 per cent of those it had scheduled that day.

The airline and the pilots' union have been negotiating over specific sections of a collective bargaining agreement since the middle of March, the lawsuit said, but have yet to agree on pilot compensation rates. The association did not respond to an e-mail attempting to confirm that negotiations were in progress.

Spirit Airlines, which is based in Miramar, Florida, is one of several budget airlines in recent years that have taken a lead on charging for service elements that customers expected to be included in the face price of a ticket. For example, in 2010, the airline announced that it would begin charging passengers as much as US$45 for carry-on bags.