Indonesian police say Friday's hijack scare on a Virgin Australia flight was triggered when an Australian passenger mistook the cockpit door for the toilet.
Matthew Christopher Lockley, 28, is in police custody in Bali.
He has claimed he was not drunk but confused.
Mr Lockley told police that he woke up and wanted a last-minute bathroom break before the Brisbane to Bali flight landed.
He insists he consumed no alcohol, saying he had only taken four Panadol, two Voltaren and drunk two Coca-Colas at Brisbane Airport before boarding flight VA41 to Bali.
The door he banged on was the cockpit door and the pilot responded by alerting Indonesian traffic controllers to a possible hijacking.
Crew members then seized Mr Lockley and handcuffed him.
Police were on stand-by when the Boeing 737-800 carrying 139 passengers landed in Denpasar on Friday afternoon after the pilot's hijack message.
Indonesian authorities are now also investigating the pilot and air traffic control staff for triggering full military procedures over the alert and closing one of Indonesia's busiest airports during the Friday peak for almost an hour.