Air Niugini has resumed flying after seven planes were grounded for not having the ground proximity warning systems, or GPWS.
It's marketing manager, Bob Martin, says Air Niugini is now awaiting a cabinet decision on whether the airline can continue flying without the system.
The Civil Aviation Authority introduced the new requirement for all planes to be fitted with GPWS by July 1 but Air Niugini has asked for an extension, despite being given five years notice.
Air Niugini's Marketing manager, Bob Martin, says flights resumed again on Sunday.
"We are under that understanding, in fact cabinet are deliberating again and that I guess it has the possibility of being changed again. But we are operating domestically until the end of October is the requested extension."
Mr Martin says its domestic flights were grounded on Saturday because CAA and the government wanted assurances over the national flag carrier's insurance policy.
Five of its F28 planes and two Fokker 100 aircraft have yet to be fitted with GPWS.