A union that represents about 55,000 flight attendants said Thursday that Delta Air Lines' flight attendants have filed a petition to hold a union representation election at the carrier for the second time in six years.

The Association of Flight Attendants-CWA said it has collected signatures from a "solid majority" of the Atlanta carrier's roughly 13,000 flight attendants.

A spokesman for the National Mediation Board confirmed that the agency received the flight attendants' petition Thursday, but had no other comment.

The move now kicks off a process lasting several weeks to a few months in which the federal agency that oversees labor elections at airlines and railroads will verify that at least 35 percent of Delta's eligible flight attendants have filed valid cards showing that they wish to join a union.

If the agency then authorizes an election, at least a majority of Delta's flight attendants would have to vote in favor of joining a union for the AFA to be able to represent employees at the largely non-union airline.

Delta's 6,300 pilots are the only large union group at the airline, which has about 48,000 employees at its mainline operations.

Last time around, only 29 percent of Delta's flight attendants voted in favor of joining the AFA.

But the AFA appears to be banking on a different outcome this time as Delta employees have struggled through multiple rounds of pay and job cuts. The tough times have now been capped by growing recession worries as well as rampant speculation that Delta is close to signing a merger deal with Northwest Airlines that adds another layer of uncertainty for employees.

Delta and Northwest are said to be in merger talks that could soon lead to the announcement of plans to create the world's largest airline. Such a deal would face steep regulatory and political hurdles, and could quickly prompt even larger merger deals among competing airlines such as United and Continental. "Definitely the merger [talk] played an important role in this campaign," said union spokeswoman Corey Caldwell.

She said a small group of Delta flight attendants first asked the AFA to help with a union organizing drive in late 2006 while Delta was still in bankruptcy, but that news of a potential merger has increased employees' concerns about job security.

"What happens when two airlines merge? The seniority lists have to be integrated," said Caldwell. She said non-union employees would be "an easy target" if job cuts follow a merger. More than 80 percent of Northwest's employees, including its flight attendants, are in unions.

Delta executives, while not confirming that the airline is in active merger talks with Northwest or any other carrier, have said in recent interviews that the airline will not go ahead with any merger unless it treats "stakeholders" fairly and positions the airline to expand its overseas network without resulting in large cuts to combined operations.

The airline also noted that federal legislation passed at the end of last year requires union and non-union employees to be treated fairly at merging carriers when integrating seniority lists.

At most airlines, an employee's seniority plays a key role in his or her job assignments, pay and job security, as lowest-seniority employees are typically the first to be furloughed during mergers or recessions.

Delta also said its flight attendants have remained better-paid than most of their colleagues at airlines represented by the AFA.

"The AFA's track record at other airlines doesn't bode well for Delta flight attendants, who, without a union, enjoy higher base rates of pay and a superior profit sharing program, along with competitive benefits and work rules," Delta said in an e-mailed statement. "Quite simply, our flight attendants deserve better than the AFA-CWA."

The company said its senior flight attendants' average pay is about $37,000 a year, compared with less than $36,000 at Northwest Airlines and almost $35,000 at AirTran Airways, both carriers whose flight attendants are represented by AFA.

The union reported similar pay totals for senior flight attendants at Delta and other airlines, who have generally seen steep pay cuts in recent years as most carriers have restructured and slashed jobs.

Delta said the union is also "eager" to win Delta flight attendants' support because it will collect about $6 million in annual dues.

Union spokeswoman Caldwell countered that the AFA's national headquarters keeps a "small percentage" of such dues, and that most are kept by the local union organization that would represent Delta's flight attendants. "They are organizing because they want their voices heard," she said.