A union representing flight attendants has all but accused Delta Air Lines of stealing a unionization vote.

On Wednesday the results of a month-long union-organizing vote by Delta Air Lines flight attendants showed that the employees narrowly rejected unionization, by a margin of 50.9 percent against to 49.1 percent in favor.

In a statement released after the vote results, the Association of Flight Attendants-CWA alleged Delta management engaged "illegal and unfair" behavior during the vote.

“We are extremely disappointed that once again, Delta management overwhelmed flight attendants with heavy handed intimidation and coercion of voters. They stopped at nothing to keep Delta flight attendants from gaining a voice and advancing their profession," AFA-CWA President Patricia Friend said in a statement.

"In the next few days, we will be submitting interference charges against Delta management for their illegal and unfair methods to sway the vote. We will ask the National Mediation Board to defend the Delta flight attendants’ right to an election free of interference," she added.

Delta flight attendants have been voting since late September on whether to unionize. Of 18,760 votes cast, only 328 votes separated the "yes" side from the "no" side.

The results seemed to surprise the Salt Lake Tribune, which reported that union organizers' exit polls showed "overwhelming support" for unionization among Delta flight attendants in Salt Lake, though no concrete numbers are provided.

Delta became the world's largest airline in 2008 when it merged with Northwest Airlines, but it stands to lose its number-one title when the United-Continental merger goes through. Northwest employees were unionized at the time of the merger; Delta employees weren't. The vote was necessary to determine the union status of the new merged airline.

James Parks of the AFL-CIO described in August what happened in the previous unionization attempt, in 2008:

When Delta and Northwest Airlines merged in 2008, more than 7,000 Northwest AFA-CWA members lost their collective bargaining rights and the 20,000 flight attendants at Delta were in the midst of a long battle to win a voice at work.

Delta management mounted a massive anti-union campaign, including harassment, videotaping and threatening union activists, says the union. Two weeks ago, the National Mediation Board (NMB) granted AFA-CWA’s request to declare that the merger created a single transportation system. As a result, the flight attendants at the merged carrier will have their first opportunity to vote for a union under new, more democratic rules.

Delta employees have voted on unionization twice before, in 2002 and 2008, and rejected it. But this was the first vote under new rules that no longer consider a non-vote to count as a "no" vote. Proponents of the rule say it removes an obstacle to unionization.

The stakes in the vote are high not just for Delta employees, but for the company as well. MarketWatch reports that a unionized shop could increase Delta's flight-attendant costs by 10 percent over the long term.

The stakes could be high for the entire industry as well. With the new voting rules in place, the Wall Street Journal reports that unions are working to organize many of the smaller airlines that in the US have not historically been unionized. Among the targets for unionization are Allegiant, JetBlue and Virgin, WSJ reports.