A poster at the site suggested that the Aussie pronunciation of “Perth” can sound a lot like “Pearce” (the airbase where they were supposed to land), making confusion easy for those who know English only as a second language.
Also Perth Intl runways are 06-24 and 03-21 and RAAF Base Pearce is 05-23 and 36-18.
Close but no cigar
That reminds me of the story I heard years ago about a guy getting on a plane that he thought was going to Oakland, and it took him to Auckland, New Zealand.