Air worthiness is determined by the FAA. In this case, the aircraft are only considered not airworthy when the flight plan calls for landing on one of those run

Air worthiness is determined by the FAA. In this case, the aircraft are only considered not airworthy when the flight plan calls for landing on one of those runways. Operating them in any other configuration is A-OK. As to why the bug exists, who knows :) Edit: Clarified slightly.