The machinists' union won an election Monday to represent about 2,900 fleet and reservations employees at AirTran Airways with 34 percent of the vote.
The National Mediation Board released results Monday that showed 994 workers favored the union, 870 opposed it, and the rest _ 36 percent of workers eligible to vote _ declined to cast ballots.
The machinists won because of a 2010 change in the rule governing such elections. Previously workers who didn't cast ballots were counted as "no" votes. But last year, the mediation board changed the rule to recognize a union if a majority of workers casting ballots favor representation.
The airline industry tried to block the change, which has given a boost to union organizing efforts. AirTran is in the process of being sold to largely unionized Southwest Airlines Co. The last major obstacle is winning approval from federal antitrust regulators.
Monday's results will make AirTran's work force heavily union too. Pilots, flight attendants, mechanics and dispatchers already belong to unions.
"As airlines consolidate, merge and partner with each other to protect themselves, the employees of AirTran realize that joining together is the best protection they have," said Rich Delaney, a district president for the International Association of Machinists and Aerospace Workers.
The machinists said union passenger-service and reservations agents at Southwest earn between $8.56 and $9.66 per hour more than their counterparts at AirTran.
Workers voted on the Internet and by phone between Feb. 28 and Monday.
The airline, part of AirTran Holdings Inc., said it would respect the right of employees to be represented by a union.