Only about 40 percent of Delta's flight attendants voted to join the Association of Flight Attendants.
Delta Vice President of In-flight Services Sandy Gordon said the vote is an affirmation of how well it has treated flight attendants.
"We're pleased with the outcome, and believe it validates what we have seen for the past 79 years, and that is our flight attendants' direct relationship with leadership is the best thing for them, as well as our company," Gordon said.
Union leaders grumbled that Delta tried to suppress voting by encouraging flight attendants not to vote.
Both sides accused the other of unfair and illegal practices. Such charges are not unusual in union elections, of course. The National Mediation Board could overturn the election if the board finds either side went too far. But this is just the first campaign for the hearts and minds of Delta's flight attendants.
If Delta's succeeds in acquiring Northwest, flight attendants for both airlines would jointly vote on whether they want union representation.
The AFA, which already represents Northwest Airlines' flight attendants, said it was heartened to get over 5,200 votes at Delta. Union spokeswoman Corey Caldwell thinks that bodes well for the next union vote.
"Today's outcome shows there's definitely the support out there for AFA representation. And Northwest flight attendants understand the significance of a union and the protection that their contract can provide," Caldwell said. "So, we're very confident that if and when a merger goes through and a new election is triggered, AFA will be representing both Northwest and Delta flight attendants."
Some labor experts expect a second vote would go the union's way. University of Minnesota labor professor John Remington thinks the numbers are in the union's favor.
Remington expects the union would win as long as it holds its votes at Delta and gets yes votes from the vast majority of Northwest flight attendants.
"I think the union is much more likely to win, given the high support for unionization at Northwest and the fact that at least 40 percent of the existing Delta employees signaled an interest in unionization."
But not everyone agrees.
Long-time airline labor consultant Jerry Glass said it'd be a mistake to assume flight attendants at a combined airline would vote for a union.
"Employees are looking at the industry differently than they have in the past, understanding that there has been a fundamental and irreversible change in the industry, its direction and what it has to do to survive and be viable," Glass said.
Northwest and Delta hope to win Justice Department approval of their merger by the end of the year.
So, it would seem a union vote for the combined flight attendants of the two airlines would come next year. Between them the two airlines would have about 21,000 flight attendants.
To win an election, the AFA would need the votes of all the pro-union Delta flight attendants plus at least 71 percent of Northwest's flight attendants. That's given the current headcount for flight attendants at the airlines.