Données issues du rapport préliminaire des autorités de l'Indonésie :
When the PK-BYK aircraft approaching point NAMP ISLAND, the PK-BYK PF saw an ATR72-600 aircraft flew through clouds from the opposite direction with aircraft nose slightly up and then the PF decided to descend with intention to avoid ATR72-600 aircraft that was maintaining 8,000 feet.
The PK-WHS pilot performed avoid manoeuvre to the right. At 01:32:06 UTC, the Bali radar screen recorded that the PK-BYK aircraft altitude was passing 8,000 feet and the horizontal distance with WON1861 was 2 Nm. Both flight continued their flight to the destination safely. The aircraft was undamaged and no one injured in this occurrence.