Avcon Industries, a subsidiary of Butler National announced that on the opening day of NBAA 2013 it received a supplemental type certificate (STC) for its 2015 Stage 3-noise compliant hushkits for the Learjet 20 series, covering most of the 350 Learjet 20-series still in service. The STC does not include those with the unmodified straight-wing and Dee Howard XR-wing–those will need a separate STC, which the company expects to tackle at a later date. Avcon brought its flight-test aircraft to the NBAA 2013 static display at Henderson Executive Airport.

Company CEO Clark Stewart told AIN that the company already holds deposits from owners who are hoping to quiet their aircraft with the hush kit. He expects the first customer aircraft installation to be complete in November.