Do I need an onward or return ticket to fly to Indonesia?

Return-ticket checks are inconsistent: some passengers are not asked, while others are required to show one. It is safest to have proof of onward travel from Indonesia before flying.

When using an automated immigration gate, there is usually no officer available to check an onward ticket. This does not remove the possibility of an airline check before departure.

The most likely checkpoint is airline check-in: a passenger may be refused check-in without a return or onward ticket, even though the document is not requested on every trip.