Complex sentence: Their main production facility, with the adjacent airfield (known in the west as Sormovo Airfield) is located on the western outskirts of the city, in Moskovsky City District, it had long been considered that district's most important industrial enterprise and main employer.
Split into simpler sentences: Their main production facility, with the adjacent airfield (known in the west as Sormovo Airfield) is located on the western outskirts of the city, in Moskovsky City District. For a long time it was considered that district's most important industrial enterprise and main employer.