New York CNN  — 

American Airlines pilots voted to go on strike Monday. Southwest pilots are holding a strike vote as well. But none of those union members will be allowed to go on strike anytime soon — if at all — under the labor law that applies to airline workers.

That law is the Railway Labor Act, which, despite he name, covers both rail workers and airline employees. Those are two of the most heavily unionized US industries, and the law places considerable hurdles in the way of any union that wants to strike. The pilots have cleared exactly zero of those hurdles so far.

If federally mediated union negotiations reach an impasse, a union can be given permission to strike. But the law allows the president to step in at the last moment and order workers to stay on the job for a months-long “cooling off periods” while a presidential panel comes up with recommendations as to how to settle the deadlock.

If the two sides can’t reach a deal during that cooling off period, the union could then go on strike — but only if Congress stays on the sideline and allows the strike to take place. But it’s possible that Congress would act to block a strike. That’s what happened with the freight railroads last December when Congress imposed a contract on the angry rail unions to keep the railroads operating.

Why pilots voted to strike

This doesn’t mean that the airline unions and their members aren’t serious about going on strike if given the chance. Most airline employees have gone years without pay raises, and they have endured extremely difficult working conditions during the pandemic.

Many unions have had members participate in informational pickets at major airports, at American pilots did Monday.

“Membership has spoken. We will strike if necessary to secure the industry-leading contract that our pilots have earned and deserve,” said Capt. Ed Sicher, president of the Allied Pilots Association, the union that represents American pilots. “Our pilots’ resolve is unmistakable. We will not be deterred from our goal.”

A history of airline strikes

There have been airline strikes in the past, but because of the hurdle, they are very rare and generally with relatively small carriers.

Spirit Airlines pilots struck for a week in 2010, but the airline was much smaller then - with only about 1% of domestic air traffic at that time.

The last time a major airline was grounded by a strike was 25 years ago when Northwest Airlines pilots went on strike for two weeks. Northwest was then the fourth largest US airline, but back then there was far less consolidation in the industry.

Since 1998, the 11 largest US airlines have merged to become the four largest carriers today, including Southwest and American. Those two, along with Delta and United, carry 80% of US air traffic between them.

Why a strike is unlikely

It’s unlikely that Congress would allow any of the four major carriers to go on strike. When Southwest had a service meltdown over the holidays that forced it to ground more than half its scheduled flights, it sparked a Congressional hearing to look into the problem.

And strike votes, in and of themselves, don’t mean that a union is going to go on strike.

Strike votes are a common negotiating tactic taken during talks. They virtually always pass by an overwhelming margin. But most negotiations are settled, even after a strike vote, without a work stoppage. Delta’s pilots approved a strike vote last year, and quickly reached a lucrative deal that gave them a 34% average raise.

American and Southwest both said this week that they are not particularly concerned about the strike vote by its pilots.

The Southwest Airlines Pilots Association’s “authorization vote will not affect Southwest’s operation or our ability to take care of our customers,” said Adam Carlisle, vice president of labor relations at Southwest. “Our negotiations continue, with talks resuming this week, and we’ll keep working … to reach an agreement that rewards our pilots.”

“We remain confident that an agreement for our pilots is within reach and can be finalized quickly. The finish line is in sight,” said American spokesperson Curtis Blessing. “We understand that a strike authorization vote is one of the important ways pilots express their desire to get a deal done and we respect the message of voting results.”