The permitted march was organized by the Service Employees International Union, which is in a dispute with an airport services company, Aviation Safeguards, which no longer has SEIU contracts.
The protest began after the airport's peak travel period of 6 a.m. to 9 a.m., and police had arranged traffic diversions, but some people driving into the airport in the early afternoon ended up in backups during various road closures over about two hours.
"People trying to make their flights were delayed," said police Cmdr. Andrew Smith.
Airlines, however, reported no major issues with passengers missing flights during the demonstration, airport public relations director Nancy Suey Castles said in a statement. Traffic through the central terminal areas also flowed smoothly, she said.
The march ended with the planned arrests of 12 people who sat down in a street and disobeyed a dispersal order, Smith said. A 13th person was arrested for investigation of shoving into a police line.
At a news conference, union members accompanied by Rep. Janice Hahn, D-San Pedro, said it was proper to stage a protest on the busy travel day because the issue affects all working people.
Hahn said she did not mind taking extra time to catch her own flight to speak on behalf of airport workers who are usually "invisible" in jobs such as cleaning planes and pushing disabled people in wheelchairs.
Mary Kay Henry, international president of the SEIU, said the union supports efforts to prevent changes to the health care plan for Aviation Safeguards workers even though the employees voted to sever ties with the union.
Jose Lobera, 77, a 10-year Aviation Safeguards employee, accused the company of splitting workers—single employees were not as concerned about an increase in family health care coverage premiums as those with dependents.
Other employees, however, said in a press release that a majority had signed petitions to leave the union and called upon the SEIU to cancel the demonstration.
Aviation Safeguards Regional Vice President Joe Conlon was quoted in the release as saying the company respected employees' right to choose representation.