STX 165 :: What does 1/2 3ATI cut out mean? Jul 23, 2014 | What does 1/2 3ATI cut out mean? 1 Comment admin on July 23, 2014 at 6:45 pm A 3ATI is a 3″ Airline Transport Indicator size cut out. 1/2 is exactly that. It is the 3ATI form factor but only half height. Sandia uses this form factor because it is both an industry standard and has a professional appearance.