After losing more than $50 billion in the decade following the Sept. 11 terrorist attacks, U.S. airlines have been enjoying some financially robust times of late.

On the front lines, airline employees are reaping billions of dollars in wage and benefit increases, plus profit-sharing plans that spell record payouts amid record income. At almost $81,000, average airline worker salaries last year were 38 percent above other U.S. private sector jobs, according to the airlines’ trade group, Airlines for America. Carriers’ wages rose 29 percent between 2010 and 2015, more than double the national average.

Yet this largesse hasn’t been spread equally. If your job is to push a wheelchair through a United terminal, or to check boarding passes for travelers headed to a Delta flight, your pay has been generally unaffected by the industry’s cash boom.

“If we really want to make America great again, our airports are a good place to start,” Oliwia Pac, a wheelchair attendant at Chicago’s O’Hare airport, said in an allusion to the president-elect’s campaign slogan. “These jobs used to be good ones that supported a family, but now they’re closer to what you’d find at McDonald’s.”

Pac and thousands of others protested at several large U.S. airports this week in a national “Fight for $15” campaign to boost service workers’ hourly wages—and to advance unionization efforts for a variety of fields where low pay is common. Beyond airports, the demonstrations included fast-food restaurant employees, Uber drivers, home health care workers, and college teaching assistants.

At airports, these low-paid positions include baggage handlers, wheelchair attendants, skycaps, and aircraft cabin cleaners . Such contract laborers perform work that ostensibly serves the airlines, but they’re employed by companies the carriers hire amid bidding contests that typically hinge on which vendor offers the lowest price.

Airlines hire outside contractors because the arrangement is more efficient for addressing each airport’s work load, explained Vaughn Jennings,  a spokesman for Airlines for America. For example, a contract firm can hire 100 employees to handle baggage for five airlines instead of each carrier hiring 25 of its own staff for the task, he said.

“The appropriate way to address wages is at the statewide or national level, so that wage scales apply to all workers equally, regardless of industry sector or geographic location,” Jennings wrote in an email. Elizabeth Wolf, a spokeswoman for Delta Air Lines Inc., which isn’t part of the trade group, said only that the carrier “supports the rights of individuals to respectfully make their voices heard.”

And the pay disparity is likely to widen.  On Thursday, Delta’s 13,000 pilots ratified a new contract offering 30 percent raises over four years. That deal will also raise pay for pilots at United Continental Holdings Inc., since they negotiated a clause in their own contract to align with Delta’s pay rates.

Outsourced airport jobs “represent the failures of a political and economic system geared towards the wealthy few and corporate profits at any cost,” say organizers of the wage fight led by the Service Employees International Union. The union says 64 million Americans earn below $15 an hour, or less than $2,400 per month for full-time employment.

“Like too many other contracted airport workers, I often have to choose between paying the rent or putting food on the table,” said Nancy Vazquez, 43, a wheelchair attendant at Newark Liberty International Airport. Vazquez said she lives with her sister’s family because she can’t afford her own apartment.

Sara Nelson, international president of the Association of Flight Attendants, said airlines are trying to stay at “arms length to this [issue] because they don’t want to take responsibility for it.” Nelson, a flight attendant at United, said carriers aren’t interested in having such duties on their payrolls and that higher wages are likely to come from city and state laws.

“They treat those jobs as expendable,” she said.

To contact the author of this story: Justin Bachman in Dallas at [email protected]

To contact the editor responsible for this story: David Rovella at [email protected]

©2016 Bloomberg L.P.

This article was written by Justin Bachman from Bloomberg and was legally licensed through the NewsCred publisher network.

Photo Credit: There's a huge pay gap these days between people who work for airlines and employees working for third parties at airports. U.S. Labor Secretary Tom Perez visited airport workers at Reagan National Airport in Washington, D.C. on June 24, 2016. David Sachs / Airport Workers United