The Rans S-9 Chaos is an American single-engined, tractor configuration, single-seat, mid-wing monoplane designed by Randy Schlitter for aerobatics and manufactured by Rans Inc. The Chaos is available in kit form for amateur construction. Production of the S-9 was ended as part of Rans' reorganization of its product line on 1 June 2006, after having been available for 20 years, but the S-9 was reintroduced in about 2009 and is again available.