The largest airline union is expanding its reach, organizing the ground service workers who have largely been left out of the airline industry's remarkable post-recession recovery.

The International Association of Machinists said that in the past 10 months it has organized more than 2,000 ground service workers at two leading providers: McGee Air Services, a newly formed subsidiary of Alaska (ALK) - Get Report  , and at United Ground Services, a United (UAL) - Get Report subsidiary.

In general, workers in the ground services industry provide baggage and cargo handling and gate service at airports where individual airlines have too few flights to hire full-time staff. Airlines employ their own ground service workers at their hubs.

"What happened in the airline industry is that back in the 1970s and 1980s, all this work was performed by airline employees," said Sito Pantoja, general vice president of the IAM Transportation Department. "But when the bankruptcies accelerated, the companies said 'we will weaken your scope clause {so} we can farm out the work.'

"Then these companies were able to hire workers at $7 an hour with no benefits."

More recently, Pantoja said, "The companies found out that with thousands of employees with very low pay, they had operations that were not as efficient. They had workers who don't care and they suffered as a result."

Union contracts are better for everyone, Pantoja said. The benefits even include a bridge to a job with the airline itself, Pantoja added.

IAM signed a contract with McGee Air Services in summer 2016. Since 2005, Alaska had outsourced its baggage handling to Menzies Aviation, a non-union firm.

Tim Klima, the IAM's airline coordinator, said the union and Alaska initially agreed to a collective bargaining agreement that covered about two dozen airport workers in Phoenix. Then workers got a chance to vote simultaneously on the CBA as well as union authorization.

"Usually companies resist the union and we have to go through the process of fighting their anti-union behavior," Klima said. "In {both of} these cases, we got the companies to agree they would treat the union without animus."

"There are dozens of ground service companies throughout the U.S.," he said. "Now McGee is one of the best contracts we have." Under the Railway Labor Act, IAM can negotiate national contracts; it does not have to negotiate on an airport-by-airport basis.

The McGee contract covers about 1,200 workers, including about 900 Seattle-Tacoma International Airport workers who signed up in March 2017. The workers, who had been employed by Menzies, were offered union jobs at McGee.

Benefits include travel privileges, improved health care benefits, a grievance procedure and increasing wages over time. The SeaTac workers were already earning $15.34 hourly after the city of Seattle passed a law increasing the minimum wage to $15 hourly.

At United Ground Express, the IAM gained about 930 workers at 31 airport locations.

United launched the subsidiary in August 2015 as a non-union company. But it signed an IAM contract this spring.

"The company was already operating when we started a campaign," Klima said. "United was satisfied with what they had negotiated with the IAM already. They thought that it was valuable to have peace with their unions, and that their employees would become more satisfied."

IAM is the largest airline union with about 65,000 active members, including 30,000 at United and 15,000 at American. Counting retirees, IAM has about 150,000 airline members.

IAM is not the only union with an interest in ground service employees. The Service Employees International Union said last week that about 500 workers at Philadelphia International Airport have voted to organize. The vote was 406-58, SEIU said.

The workers, employed by contractors Prime Flight and Prospect at Philadelphia International Airport, include baggage handlers, wheelchair agents, skycaps, line queues and other passenger service workers. The next step is to negotiate a contract.

Asked whether there is conflict with IAM, SEIU spokeswoman Leslie Kamstra said, "The airport workers' movement, like all SEIU efforts, is about improving jobs for all workers so they can provide for their families.

"Airport jobs used to be good jobs that allowed workers to support their families, but over the past 15 years, most contracted airport workers saw their wages stagnate or decline," Kamstra added. "Airport workers are joining together to change that."

This article is commentary by an independent contributor. At the time of publication, the author held no positions in the stocks mentioned.