About 600 members and supporters of Service Employees International Union marched peacefully Tuesday, chanting and waving union banners along Philadelphia International Airport's departures roadway and demanding higher wages and better working conditions for nonunion PHL workers.

Six busloads of demonstrators wearing purple "32BJ SEIU" T-shirts arrived in buses outside Terminal A and marched to Terminal F. They were escorted by Philadelphia police and sat, at one point, in front of Terminal C for speeches.

Many marchers were from out of town - as far away as Virginia, Connecticut, Pittsburgh, and New York - and said they came to support wheelchair attendants, sky caps, aircraft cabin cleaners, and bag handlers who work for airline subcontractors and are demanding $15 an hour. (The bag handlers work at luggage carousels and help passengers get their bags to the curb for tips. A different group of baggage handlers who work directly for the airlines handles bags on and off airplanes.)

Pablo Palino, who works for a cleaning company in Manhattan and is a Local 32BJ member, said he and many others came to help the Philadelphia workers.

"We support the people for what they want," Palino said.

Michael Anderson, a 32BJ member who works in security at the Navy Yard in South Philadelphia, said, "I'm here because security and all employees should have equal pay and equal rights."

SEIU 32BJ general counsel Walter M. Meginniss Jr. notified the PHL workers' employers Tuesday that some employees planned to walk off the job and stage "a short strike" between 11 a.m. and 2 p.m., and then would return to work their regularly scheduled shifts.

SEIU organizes airport rallies, which it often calls "strikes," every couple of months, usually around holidays and at busy travel periods. Tuesday's demonstration was timed ahead of the Democratic National Convention to protest unfair labor practices and low wages paid by airline contractors Prospect, PrimeFlight, and McGinn Security, organizers said.

SEIU is trying to organize the 1,000 workers in a union.

Beginning July 1, 2015, the workers won an agreement with the city to be paid $12 an hour, in keeping with a "living wage" standard approved by Philadelphia voters in May 2014. Before that, they earned as little as $7.75 an hour plus tips.

Now, the workers are demanding $15 an hour and voted last week to authorize a possible "strike" during the convention.

The permit obtained by SEIU for Tuesday allowed the workers to picket and hand out informational leaflets outside Terminals A, B, C, D, E, and F. The permit stated that no more than 22 "picket leafleters" may congregate at any one time outside each terminal, airport spokeswoman Mary Flannery said.

As of Tuesday, SEIU had not obtained a permit to picket during the Democratic convention.

American Airlines, which operates 70 percent of flights at Philadelphia International, said the protest - like prior demonstrations by SEIU - would not disrupt flights or operations.

"American Airlines is focused on giving our customers the best possible service in Philadelphia," spokeswoman Victoria Lupica said. "Our direct employees are already unionized with the company's full support. SEIU endorsed the agreement reached last year between American and the City of Philadelphia, which provided a $12-per-hour minimum wage with four years of increases for the employees of our vendors. Protest of that agreement such a short time later seems misguided."

Mayor Kenney issued a statement after last week's strike vote, saying that the airport workers "deserve a living wage, paid leave, and the right to form a union without interference from their employer."

Kenney said, however, that "we don't anticipate these demonstrators will interfere with airport service during the DNC."

The mayor noted, "The city has very limited legal ability to compel subcontractors" to pay higher wages.

"The administration has held several meetings with all parties, one as recently as last week, to urge subcontractors to achieve labor peace," he said. "This administration will continue to be committed to advancing economic justice and fairness for the dedicated workers at PHL."