From The Guardian Online:
They are the amazing pictures that were beamed around the globe: a handful of warriors from an 'undiscovered tribe' in the rainforest on the Brazilian-Peruvian border brandishing bows and arrows at the aircraft that photographed them.
Or so the story was told and sold. But it has now emerged that, far from being unknown, the tribe's existence has been noted since 1910 and the mission to photograph them was undertaken in order to prove that 'uncontacted' tribes still existed in an area endangered by the menace of the logging industry.
While I didn't write about it when this story first surfaced, I did have some doubts about it. They were spawned by the now famous picture with the red painted warriors firing their bows and arrows up at the plane. It didn't strike me as authentic.
As for whether or not there are still "uncontacted" tribes in the Amazon, I guess it is possible there are isolated pockets of them here and there who have never met outsiders before, but they surely know that they are not alone. I am sure some of them have spoken with people in other tribes and found out about visitors to the forest and this can't have been the first time they ever saw an airplane.
Another thought I had was "Oh shit, now some Christian missionaries are going to try to find them so that they can 'save' them."