A researcher at Human Rights Watch in Jakarta is calling for the immediate release of the hostages including a New Zealand pilot being held by a rebel group in Indonesia's Papua region.
The rebels in Highland Papua are threatening to execute Susi Air pilot Phillip Mehrtens if their demands are not met.
Five other people were also believed to have been taken hostage in the attack.
The West Papua National Liberation Army has posted an ultimatum on social media demanding Jakarta negotiate with them over independence for the region.
"Pilot is still alive and he will be held hostage for negotiations with Jakarta, if Jakarta is obstinate, then the pilot will be executed," the statement read.
"We will take the New Zealand citizen pilot as hostage and we are waiting for accountability from the Australian Government, the New Zealand Government, the European Union Governments, and the United Nations, because for 60 years these countries have supported Indonesia to kill Indigenous Papuans."
Researcher Andreas Harsono knows the main spokesperson of the rebel group Sebby Sambom after decades of research in the field.
He made a call to him personally to let the hostages go.
"I call on this group to immediately release all of the hostages including the pilot - it is a crime to kidnap anyone including this pilot," he told RNZ Pacific.
"I do not know how to measure the seriousness of such a threat but this is a hostage situation, things could be out of control. So the best way is to negotiate and ask them to release the pilot."
Harsono noted the difficulties in New Zealand attempting to negotiate with the group, particularly given their demands.
"I don't think it is easy or even internationally accepted to pressure the New Zealand government to negotiate for West Papuan independence from Indonesia.
"It is way too complicated for any country in the world including New Zealand to negotiate the independence of this particular territory but of course the Papuan people have suffered a lot and the Indonesian government should do more to end impunity and human rights abuses in West Papua.
"But this is a hostage situation. The most important thing is to call on this group to immediately and unconditionally release all of the hostages including the New Zealand pilot."
Harsono said he does not know whether the passengers have been taken hostage, nor does he know if they are indigenous Papuans.
"The area is very remote, only certain people go there, mainly construction workers, and there were killings against Indonesian workers back in 2018," he said.
Police encounter difficulties looking for pilot
Indonesian authorities say it's facing difficulties locating Merhtens because of the lack of telecommunications facilities in Paro District and the absence of any Indonesian Military or police post in the area.
Jubi TV quotes Papua Police spokesperson Ignatius Benny Ady Prabowo saying his party continued to track the whereabouts of Mehrtens and are preparing to go to Paro District.
He said that before the burning of the plane, rumours had been circulating that a rebel group had threatened 15 construction workers who were building a health centre in the district.
"The New Zealand embassy in Indonesia is working on the case," New Zealand's prime minister, Chris Hipkins, told Radio New Zealand.