FAA Approval of Non-Halon Replacement Portable Fire Extinguisher OLATHE, Kan., Aug. 21, 2025 /PRNewswire/ -- Avcon Industries, Inc. and its affiliate Butler Avionics Inc., subsidiaries of Butler National Corporation (OTCQX: BUKS) and leading manufacturers and systems integrators for special mission aircraft modifications, announce Federal Aviation Administration (FAA) Supplemental Type Certificate (STC) approval for the installation of non-halon portable fire extinguisher replacements in Learjet Models 24, ...