Union leaders are spearheading an effort that includes Georgia congressmen and Lockheed Martin officials to award a new government contract for building the C-130 aircraft in Cobb County.

About half of the 5,000 workers at Lockheed Martin's plant in Marietta work on the C-130, according to the International Association of Machinists and Aerospace Workers, which represents many of them.

The current C-130 program runs through 2020. That contract calls for construction of 83 planes, the company said Thursday.

Like many large defense projects, production of the C-130 is spread across the country – and through many congressional districts. In this case, the program for the huge plane, which began in the early 1950s, involves 32,000 employees and 570 suppliers in 41 states.

More than 2,500 C-130s have been built in Marietta since the early 1950s.

About half of 5,000 workers at the Lockheed plant are working on the C-130, according to the International Association of Machinists and Aerospace Workers, which represents many of the Marietta workers.

The C-130 was meant to carry supplies as well as troops and to deliver them via air drop or short runways.

But it has yeoman's work across the world on missions of both war and humanitarian relief. It has been praised by the likes of Popular Mechanics as an extraordinarily well-designed plane.

A letter signed thus far by at least 48 members of Congress urges the Trump administration and Defense Secretary James Mattis to endorse an extension of the C-130 program. That letter was still in draft form Thursday, but if completed Friday,  it could be delivered to Mattis.

If a new, five-year contract is not signed, the government is expected to still need new C-130 aircraft, but they would be ordered piecemeal.

Lockheed says such short-term orders are much more costly.

The company argues that the dependability of a longer commitment saves money and that those savings can be passed through to the government. Over the course of the current program, costs to the government are $600 million less than they would be buying year to year, according to Robert Martinez Jr., president of the International Association of Machinists and Aerospace Workers.

That is 10 percent of the program’s cost.

Lockheed Martin has proposed a five-year plan to deliver C-130Js to the U.S. Air Force, Navy, Marine Corps and Coast Guard. The Defense Department has plans for about 100 more C-130 aircraft, according to the letter being circulated among Congress members.

“The (extension) would provide important stability to the program's supplier base while supporting over 30,000 good-paying American jobs,” Martinez said in a statement.

Government officials are reviewing the proposal, according to a statement from Lockheed Martin.