COATESVILLE (AP) – Lockheed Martin will close its Sikorsky helicopter plant in Chester County, saying it has made a final decision on it amid a downturn in the commercial helicopter sector. The Maryland-based company said despite working with its customers and federal, state, and local officials, it had been unable to secure enough additional work to sustain operations at the Coatesville plant. It will consolidate the work in other Lockheed Martin locations. The company expected this would result in a reduction of about 240 employees.