AIT was introduced with PR announcing how much better they would be for people with metal implants that alarm the WTMD since these implants would not alarm the AIT. At that time, AIT was optionally used as a secondary screening to resolve WTMD alarms.

However, going through the AIT does not guarantee you won't receive a pat-down. If anything alarms the AIT / an abnormality is spotted, you will receive a pat-down to resolve the alarm.