Lockheed Martin’s Sikorsky helicopter plant just outside Coatesville is set to close next March, ending about 360 jobs at one of the western suburbs’ major industrial employers.

The company had planned to close the plant in Chester County’s Sadsbury Township in 2019, as orders from its main customers in the oil and gas industry dried up amid crashing energy prices.

That shutdown was averted as pressure from then-President Donald Trump, U.S. Rep. Chrissy Houlahan (D., Pa.), and other officials persuaded the company to keep the plant busy, in part by finishing the Marine One helicopters that carry the president.

But the reprieve is over, Lockheed Martin confirmed.

About 240 people are expected to lose their jobs, with 120 more offered a chance to relocate or work remotely, according to the company and Houlahan’s office. Lockheed Martin, a major U.S. military contractor, also has facilities in King of Prussia, Johnstown, Pa., and Moorestown.

“After spending the last two years working with Lockheed Martin, White House officials in two administrations, and state and local partners to find ways to enable the plant to continue operating, I am frustrated and disappointed that we find ourselves here,” Houlahan, whose district includes the Sikorsky plant, said in a statement Thursday disclosing the planned closing.

A Lockheed Martin spokesman confirmed the decision in a statement, saying the company “has made a final decision to exit its Coatesville facility and consolidate the work in other Lockheed Martin locations due to a downturn in the commercial helicopter sector.”

The company said it was unable to secure enough work for the facility and has been in touch with Gov. Tom Wolf, the White House, and U.S. Commerce Secretary Gina Raimondo. A spokesman said the company aims to “ensure training and reemployment opportunities for all existing employees.”

The former Sikorsky company took over the non-union plant it called the “Heliplex” in 2005, when it purchased the former Keystone Helicopter Corp., which had finished and repaired Sikorsky copters on the site.

The Philadelphia region is a historic center of helicopter production, one of the last heavy industries to survive the exodus of steel, railroad, and electrical equipment and petrochemical plants in recent decades.

It is also home to the Boeing military helicopter plant in Ridley Park, which employs more than 4,000, including United Auto Worker union members. There is also the nonunion Leonardo (formerly AgustaWestland) helicopter factory in Northeast Philadelphia, which employs about 600.

A 2014 state grant helped pay for the Sikorsky expansion. But Sikorsky’s purchase by Lockheed Martin the next year left the plant competing internally for orders against larger plants in Connecticut, New York, and elsewhere.

Guy Ciarrocchi, president of the Chester County Chamber of Business and Industry, called the announcement “deeply disappointing” and said the group will help employees find work and to find new uses for the 20-acre complex.

“We will not accept a vacant property sitting in the Coatesville area,” Ciarrocchi said.

“This is a significant loss for the region,” said Gary Smith, who heads the Chester County Economic Development Council.

But he also noted that skilled manufacturing workers such as those on the Sikorsky force are now in “high demand” and that there’s a shortage of industrial sites in the area, so there’s hope that both staff and plant will be busy again soon after the closing.

Chester County has scheduled a manufacturing and trades industry job-recruiting fair for next Wednesday, the county commissioners said in a statement. They promised to “find skilled jobs for every Sikorsky employee who wants to continue working in Chester County.” They also predicted that the 22-acre Sikorsky site will attract developers.

The Coatesville-area plant has produced several Sikorsky models over the years, including a version of the VH-92 aircraft that is the foundation for helicopters used by presidents and other White House officials, commonly called Marine One.

In 2019, when it first announced closing plans, Lockheed Martin had 465 employees on its 24-acre campus.