The wreckage of a small plane that went missing six weeks ago in the northern Philippines was found in jungle on Thursday, with all six people on board confirmed dead, rescuers said.

The Cessna plane took off from Cauayan airport in Isabela province on January 24 on a route that would have taken it across the Sierra Madre mountain range.

It failed to arrive at the nearby Maconacon airstrip on the Pacific coast.

"Sadly, there were no survivors," civil defence officer Constante Foronda told reporters after the crash site was found in thick forest on the mountain range.

Difficult terrain means it will take rescuers three days to take the bodies of the pilot and five passengers to the nearest town, Divilacan in Isabela.

The discovery comes as a search operation continues for a medical evacuation helicopter that went missing on March 1.

The aircraft was flying a patient from the remote Mangsee Islands to a hospital on the western island province of Palawan.

Five people were on board, including an American pilot and American nurse.

A pillow belonging to the patient and the shoes worn by the nurse have been recovered from the water.

Another Cessna plane crashed on an active volcano in the central Philippines on February 18, killing all four people on board, including two Australians.