JetBlue Airways Corp. pilots voted to join the Air Line Pilots Association, ending the carrier’s status as the biggest U.S. airline without a union and erasing a gain in the stock.

Collective bargaining may bring higher costs as New York-based JetBlue negotiates pay rates and work rules to cover all its pilots. Now the fifth-largest U.S. carrier, JetBlue began flying in 2000 and has long cast itself as a model of labor relations in an industry known for discord.

ALPA won support from 71 percent of pilots eligible to vote, according to the union. Once the National Mediation Board authorizes the union as the pilots’ representative, JetBlue and the union will organize committees to craft a contract, Chief Executive Officer Dave Barger said in a statement.

“JetBlue pilots have voted for ALPA representation so that we have the ability to improve our professional careers,” said Gustavo Rivera and Rocky Durham, co-chairmen of the organizing committee at the airline. “We also want to work with management to ensure we continue to contribute positively to JetBlue’s success.”

JetBlue fell 2.4 percent to $8.55 at 3:16 p.m. in New York. The shares rose as much as 2.1 percent earlier, then tumbled after Washington-based ALPA commented on the balloting.

The airline said today it has 2,529 pilots, while ALPA said the total was more than 2,600.

It was the third such vote by JetBlue pilots, who turned down the creation of an independent bargaining unit in 2009 and again in 2011. The International Association of Machinists and Aerospace Workers couldn’t muster enough support in 2006 to represent baggage handlers.

At least 50 percent of JetBlue’s pilots had to support the union before the National Mediation Board agreed to set the election.