Question: What is the name of the commercial airline that serves this public use airport (owned by the city and county) near the city in Valley County, Montana with a population of about 3,400 as of 2015?
Sentence (from "Brookings Regional Airport"): Starting from September 2009, the airport is no longer served by a commercial airline after the United States Department of Transportation ended the subsidy for this airport's Essential Air Service program.
Relevant evidence: No