WASHINGTON ( TheStreet -- As Congress prepares to consider legislation making it easier for unions to sign up workers, about 750,000 unionized transportation workers watch from the sidelines, knowing they would receive no immediate benefit.

That's because the Employee Free Choice Act, now pending, affects only workers covered by the National Labor Relations Act. Transportation workers generally fall under the Railway Labor Act, which makes organizing tougher and strikes less likely, on the theory that any breakdown in transportation services would be overly harmful to commerce.

Still, transportation unions and workers are closely watching what happens to the Employee Free Choice Act, says Robert Roach, general vice president of the International Association of Machinists, the largest airline union.

Robert Roach

"If the law is changed under the National Labor Relations Act, that will fuel a debate we are having regarding the RLA election process, which currently is unfair," Roach says. "The RLA is governed and administered by the National Mediation Board, which at some point could alter its regulations. So the Employee Free Choice Act is important because it will help to form that debate, as to what changes if any could be made.

"To start that process, we would have to petition the board to make changes," he says.

The biggest problem with the RLA election process, Roach says, is that for a union to win it must have 50% plus one of all the workers in a bargaining unit, not just all the workers who vote. Not only does that mean not voting constitutes a no vote, but also, unions sometimes have to round up legions of laid-off workers and urge them to vote.

"If Barack Obama had tried to run for president under the RLA, he would not have been elected unless he had a majority of all eligible voters, not just those who voted," Roach said. "Those who chose not to vote did not influence his election."

Organized labor backs the Employee Free Choice Act despite the likely scuttling of the controversial card check provision, which would have enabled unionization as soon as unions collect signed cards from a bargaining unit majority. Currently, employers can require a secret-ballot election after the cards are submitted.

Even without card check, the law helps labor, primarily because it removes a provision enabling a company to seek union decertification if a contract is not signed within a year of a unionization vote. The provision encouraged stalling by anti-union companies, labor maintains.

The differences between the National Labor Relations Act and the Railway Labor Act play a role in two current labor disputes.

At Delta ( DAL), which merged with Northwest in 2008, both the IAM and the Association of Flight Attendants want to continue to represent members whom they represented at Northwest. But Delta has been largely non-union, so the unions' effort to organize workers at the combined airlines could be this year's major organizing effort.

Ed Gilmartin, attorney for the Association of Flight Attendants, says the RLA hinders the effort in several ways. For one, the NLRA enables workers to organize on a location-by-location basis, while the RLA requires companywide voting. New Delta has about 20,000 flight attendants. "The bigger the group, the harder it is to win," Gilmartin says.

Moreover, while the NRLA requires that the company provide the names and addresses of eligible voters to the union, the RLA generally does not. And, of course, the RLA requirement for 50% plus one of a bargaining unit presents a barrier. "At Delta, we think there will be 19,000 eligible voters, so we would need 9,500 plus one," Gilmartin says. Under NLRA rules, if 10,000 were to vote, the union could win with 5,001 votes.

However, the AFA has the option to ask the National Mediation Board to permit a standard yes/no balloting procedure, as occurs under the NRLA. It made such a request to the NMB before a 2008 election at Delta, and was turned down. "We asked for it last time, and there is no reason why we wouldn't ask for it again, since the composition of the board has changed" under the Obama administration, Gilmartin said.

Delta spokeswoman Chris Kelly says Delta would not support a change. "The NMB has had voting rules in place for more than 70 years," she says. "Those rules have been supported both by labor organizations and carriers. Changes to the voting rules have been proposed from time to time and have consistently been rejected."

Meanwhile, FedEx ( FDX) has been resisting an effort by some members of Congress to change the classification of its airline, FedEx Express, from an RLA company to a NRLA company, which is the way competitor UPS ( UPS) is classified.

Fed Ex has said it objects to the location-by-location organizing allowed under the NLRA because it "allows you to take a small group of employees and use them to destroy customer service," says spokesman Maury Lane.

However, Lane says that already, many of FedEx's 230,000 U.S. workers are covered by the NLRA and have chosen not to unionize.

The airline division, FedEx Express, has 143,000 workers who are covered by the RLA. "You don't need third party representation at FedEx," he says. "We have a people first culture that creates a much stronger trust between our colleagues and management."

-- Written by Ted Reed in Charlotte, N.C..