A federal labor board cleared Delta Air Lines of allegations that it interfered in a union election by its customer service workers.
The ruling by the National Mediation Board wraps up the biggest union vote in recent years with a victory for the airline, which had fought hard against voting changes that favored the union. Once it lost that fight it sent strong messages to workers that they would be better off without the union.
Most Delta workers have not belonged to unions, but the airline absorbed heavily-unionized Northwest in 2008. Votes were called to sort out whether unions would represent the combined groups or be forced out. The unions lost.
This is the fourth case where the mediation board dismissed allegations that Delta interfered in union votes. The other groups that brought claims were baggage handlers, flight attendants and stock clerks.
The ruling on Friday dealt with a November 2010 vote covering more than 15,000 workers including ticket agents, cargo workers who deal with customers and reservation sales workers. Of 12,518 workers who voted, 70 percent rejected the union.
In response to the ruling, Delta said it will immediately equalize benefits, pay and work rules for customer service workers. That will mean raises for most of the former Northwest employees.
The International Association of Machinists and Aerospace Workers had claimed that workers were influenced by Delta's promises of pay raises once the elections were over, and by the risk that Delta would monitor online employee voting from company computers.
The federal board found that Delta had been promising raises since before the election began and that there was no evidence that the airline monitored how workers voted.
Pilots at both airlines were already represented by the Air Line Pilots Association before Delta bought Northwest.
Shares of Atlanta-based Delta Air Lines Inc. rose 32 cents, or 3.9 percent, to close at $8.50.