MADISON, Wis. (AP) – A proposal that would exempt aviation companies in Wisconsin from having to pay sales taxes on aircraft maintenance parts and labor is up for a vote in a Senate committee.  The Republican-backed bill would benefit companies like Gulfstream in Appleton and Cessna in Milwaukee. Those companies and others say having to pay the sales tax puts them at a competitive disadvantage because aircraft owners are taking their business to other states that don’t charge the tax.  The Senate’s Economic Development Committee planned a Tuesday vote on the bill sponsored by Sen. Mike Ellis.  Ellis says the bill would cost about $3 million a year in lost revenue, but it would generate more than twice that much in increased business for the aviation companies.