>We must not contact them, unless they want to contact us.

And how do we tell?

They can't know about us unless they... know about us (contamination: our existence, and any visual differences). They can't contact us unless they know where we are (contamination: we're watching them, and they see us doing so). Then they can't express desires until we understand each other (contamination: language and ideas). At that point, you've already significantly altered their culture, at least for the individual(s) you directly dealt with, and any they told. If we "must not contact them", then we must not contact any, because every person is part of a group, and arguably is a group of one, so you've already contaminated a person, a group, a sub-culture, a unique society that will never be the same again.

We either force contact, or we deny them the knowledge of our existence. There is no middle-ground, because any step away from zero contact is contact. Inaction is just delay of choice; what happens if they literally walk in a straight line until they hit a city? We are forcing contact by our mere existence, we could pick up the city and move to avoid contaminating them against their choice, since if they didn't know about us they couldn't have chosen to contact us.

Your last paragraph, if analyzed, contains a false assesment. If they walk in a straight line and contact us, and then they don't return to their way of life because they want to keep that contact, then we can be certain they want to communicate with us. We can CHOOSE to stay away. There's nothing that states we MUST communicate or have relationships with all human beings, nor step onto EVERY land until everything's explored and divided. Just let them be, do not interfere.

Really? What if they're just out walking and are unaware of the existence of other humans? Finding a city when you think your group is all there is would be rather "contaminating". And you've still contaminated that one; if they bring back that information, you've allowed contamination of the culture as a whole, the same as if you went yourselves, except you get to sit back and lie about how you had nothing to do with it. Unless you wish to state that an individual can and does accurately speak for a group, especially a group you know almost nothing about except what that individual has told you? What if they're the anarchist of the group?

And if we were to know if they think other humans than themselves / those they immediately interact with exist, we've probably exposed ourselves to them, as that would be hard to know through un-detected observation alone.

Our existence is interference if they become aware of it. Absolute non-interference is impossible if they ever become aware of us in any way. If we "must not contact them" unless they want it, we cannot impose ourselves on any who do not wish to contact us, which means complete isolation until they magically express their desire to contact that which they cannot know exists.

My point is that "We must not contact them, unless they want to contact us." is a logical impossibility, not something one can actually achieve, and it makes no sense to hold such an impossibility as an ideal.

"What if they're the anarchist of the group?"

What if they are? Can you see the diference between giving them, a group with far fewer resources to defend themselves, the chance to remain isolated if they want it so, or contact us as well, against forcing our presence there?

"Our existence is interference if they become aware of it"

I concede you that point. Can I rephrase "must not contact them" with "should minimize points of contact from our side"? Those planes have their purpose: to make us aware of their presence, because we're about to wipe out their environment. Should we keep our distance? Yes. Should we do nothing and let companies run them over? No, absolutely not. Then I go for flying over them and take pictures.. It's the lesser of two evils.

There's no magic. Once they discover us, instead of we discovering them, they can take the step to communicate wth us.

It makes you wonder what they were thinking when they saw the plane flying around over their heads. In almost every shot of the tribe, they were all standing and staring. I doubt it is the first time they have seen some sort of modern technology, but it certainly isn't common.

Modern man is taking away their land to oil drilling and logging. Personally, I think we should treat it as tribal leaders once did. We are the enemy. If we want to preserve them, then we should not study them as subjects either. That is their land, their home. Let them be.

It sounds like they would have seen planes many times as this guy has been following them for 20 years. It would be interesting how they perceive the planes, they may see them as some kind of god watching over them.

Hard to say since it's unlikely to be the same plane, they might think it's either multiple beings. I'd suspect more that they think it's a giant bird than a god though.

>they may see them as some kind of god watching over them

Or they may see them as a manufactured tool for flying