The Australian Transport Safety Bureau says a Qantas flight crew momentarily did not know their plane's location while trying to land at Canberra airport last year.
The Boeing 737 was flying from Sydney to Canberra in wet, cloudy and dark conditions last February.
The ABC reports the instrument landing system at Canberra airport was not working due to scheduled maintenance, so the flight crew made an alternate approach without vertical flight path information.
But the ATSB found the automatic flight system was in the wrong mode. The plane descended below the minimum safe altitude, causing the flight crew to lose awareness of where they were.
Once identified, the crew corrected the approach and landed safely.
But the ATSB says any loss of situation awareness increases the risk of a crash. It says the incident highlights the importance of situational awareness and the need for crews to monitor their plane's flight profile when descending.