DOVER, N.H. – Following a 45-year decline in membership, unions may be making a comeback.

Recent strikes by United Airlines, Verizon and Firestone workers may mean unions have turned a corner.

“You can point to the last five years as what may be a historic turning point after three decades of decline,” said Michael Hillard, an economist who studies labor trends at the University of Southern Maine. “There’s a tremendous amount of interest and momentum out there.”

In 1997, 16.1 million people belonged to a union. Last year that figure inched up slightly to 16.5 million, despite attrition and an expanding workforce.

“We’ve actually gained members and we’ve turned this thing around,” said Mark McKenzie, president of the New Hampshire AFL-CIO. “If you consider that you lose membership all the time, that’s actually a pretty significant gain.”

While unions say their comeback is good news for workers, employers disagree. Organizing drives by Teamsters Local 340 at the Pratt and Whitney plant in North Berwick, Maine and L.L. Bean in Freeport, Maine are both facing stiff opposition.

“We don’t see that there’s any advantage to putting a third party between us and our employees,” said Pratt and Whitney spokesman Mark Sullivan. “We don’t think that a union is going to add anything to the welfare of our employees or to the competitiveness of our plant.”

L.L. Bean spokeswoman Mary Rose MacKinnon shared similar sentiments.

“We firmly believe that L.L. Bean employees are better off without a union and that we can best solve problems working together,” she said.

Despite the unions gaining members and the recent success of striking Verizon workers, unions have a long way to go to match their former stature. In 1954, unions represented nearly 40 percent of private-sector workers. In 1999, only about 14 percent of the workforce claimed membership in a union or employee association.

That downward trend could explain why labor lost its political clout years ago. Once a force to be reckoned with, unions haven’t had major influence over elections since 1968, said Hillard.

Labor organizers still point to statistics showing that organized workers earn more than non-organized workers, but add that workers are increasingly looking to unions for leadership on social security, prescription drugs and other issues.

Unions have also become more savvy in their organizing efforts, forming partnerships with community and church groups and diversifying its representation, McKenzie said. Today’s organizers are just as likely to be women as they are to be men, and black, Asian and Latino faces are increasingly common.

“I think if you look at what we’re trying to do, [you see] we’re trying to build a strong grass-roots movement,” said McKenzie. “More and more people are looking toward the labor movement as a way to improve their lives and make things better.”