Airport workers, union members, clergy and others rally for a wage of $15 an hour at Ronald Reagan National Airport on Nov. 29. (Matt McClain/The Washington Post)

Contract workers at Dulles International and Reagan National airports will walk off their jobs sometime this month, joining a growing number of workers across the country staging strikes as part of a national push for better working conditions and a $15-an-hour “living wage.”

Workers voted Thursday to authorize the walkout. No date has been set for the action and it is not clear how long it would last, but a spokesman for the group said it will likely happen before the end of the month.

The action comes as airlines and airports gear up for Christmas holiday travel.

“This was not an easy decision to make,” said Jaime Contreras, vice president of Service Employees International Union Local 32BJ for the Washington area, which is helping organize the action. “But the overwhelming majority have made a choice to strike because they are fed up with making poverty wages and these employers are not listening to them.”

The workers include wheelchair attendants and baggage handlers who work for Hunt­leigh USA. According to union officials, the Texas-based company, which contracts directly with the airlines, employs roughly 400 workers at the two airports.

Officials at Huntleigh did not respond to calls and emails seeking comment.

The planned strike is one of a growing number of job actions designed to raise awareness about the plight of minimum wage workers at airports, in the fast-food industry and in other service-focused jobs.

Contreras said some workers at Dulles and National make as little as $6.15 an hour, plus tips. He said many have to work two jobs to support their families, and some sleep at the airport because they don’t have enough money to pay for transportation to and from work.

“We work very hard to ensure that travelers have a safe and clean airport, but we are ready to go on strike to ensure we can provide for our families,” said Aynalem Lale, a wheelchair dispatcher at Dulles. “If I made $15 an hour, I wouldn’t have to work two jobs and would not have to sleep at the airport between jobs.”

Last month, hundreds of contract workers staged a one-day walkout at Chicago’s O’Hare International Airport. They were joined by fast-food workers and Uber drivers across the country. O’Hare officials said the strike did not have an impact on airport operations.

It is not clear what effect the workers’ actions will have on operations at Dulles and National. Rob Yingling, a spokesman for the Metropolitan Washington Airports Authority, which manages the two airports, referred all calls to the individual airlines.

“We are taking the necessary steps to ensure prompt service to our customers,” Charles Hobart, a United spokesman, said via email.

Airport workers in other cities, including major hubs such as Los Angeles and New York, have been able to win concessions. In South Florida, Broward County officials voted in fall 2015 to extend a living-wage ordinance to contract airline workers, increasing wages by more than $3 an hour for some of them.

Workers doing such jobs once worked directly for airlines or airports, but many are now employed by outside contractors. Advocates say the trend has led to lower wages and fewer benefits for workers, many of whom are immigrants and members of minorities.

According to the union, between 2002 and 2012 outsourcing of baggage porter jobs more than tripled, from 25 percent to 84 percent, while average hourly real wages for both directly hired and contract workers declined 45 percent, from more than $19 an hour to $10.60 an hour.

This is the first time that contract workers at Dulles have agreed to strike.

In March, wheelchair attendants, skycaps, baggage handlers, checkpoint agents and ­cabin cleaners for two contractors at National Airport staged their first-ever walkout. Workers in nine other cities, including Seattle, Chicago, Boston, Philadelphia and Newark, also staged job actions.

Workers at National and Dulles also have targeted the airport authority’s board of directors, demanding that it require firms that do business with the airports to pay workers a minimum of $15 an hour.

The authority has a living-wage policy that applies to airport contracts but not to companies that contract directly with individual airlines, as is the case with Huntleigh. Currently, more than 2,000 workers at National and as many as 4,200 at Dulles work for such companies.