Sdruvss,
The posts by ATC Watcher, marciovp and A310driver say a lot of what I would have said in reply. I will not repeat here points they have made; I supplement them.
It seems to me that your concern has a number of components. Firstly, if I may say so, you don't seem to understand the contract between airspace users (pilots) and air traffic control under Instrument Flight Rules: what a clearance is and means, what a flight plan is and means, what takes priority over what and when. This is not trivial stuff. And, for example, it forms a large part of training for instrument flight. But it is stuff that IFR-rated pilots and controllers deal with every day, so if you are new to all this, please bear in mind that you are discussing with people with considerable expertise, and please don't take it badly if people flatly contradict you on some matters.
But it is also unfortunately not unambiguous. International misunderstandings over the roles and abilities of pilots and controllers have arguably contributed to two recent crashes: the 2002 Überlingen midair collision, and the 2006 Sochi CFIT, so international agreements play a role also. The Überlingen report in particular went into great detail over the differing guidance that may or may not have been in force or have played a role in that midair. That section of the report makes very sobering reading. I recommend it.
Furthermore, even in cases in which guidance is not unambiguous, it may be obscure. I give examples of three jurisdictions.
In the U.S., the Federal Aviation Regulations are published and readable. Indeed, you can get them on the WWW, and they are in a widely-used international language, namely English.
Move to the U.K. The corresponding law is called the Air Order; it will fill an entire bookshelf; it is written in language, some of which has a precise meaning which is only understood by professionals conversant with English law. The CAA provides some readable guidance booklets, called CAPs, and what is in the CAPs is used as a basis for what a pilot should know about the U.K. aviation law and rules. Now, suppose you wanted to fly to the U.K. in your bizjet, and you wanted to know about the rules. What would you do? Try to order a CAP? Which? Where do you find the list? How do you find out which CAP has the information you want?
Move to Germany. You can get the law on the WWW, It is called the LBO. But reading and interpreting legal German is something that most Germans cannot do, let alone people who do not speak or read German. It has taken me years of being here, and participating in legal proceedings, to gain an understanding of what specific meaning certain legal phraseology has. The LBO is no different. And I can assure you that there are plenty of German pilots who do not understand quite what the LBO says. So if you consider an incident in which some Russian under control of a Swiss hits a Belgian plane in German airspace, it is a fair bet that none of the participants actually understood the law governing their unfortunate interaction.
With this rather long-winded discursion, I simply hope to have indicated that it is simply not humanly reasonable to expect foreign pilots to understand all aspects of local aviation law, in most places except possibly the U.S.
That is why ICAO, and ICAO procedures, play such an important role. But in some cases (Überlingen), having ICAO procedures could be seen, not as cutting through the darkness with light, but as adding *yet another* layer of mutually partially contradictory guidance.
So how might this apply to the Amazonas midair collision?
If ATC Watcher and his organisation are unable to get an answer from the Brazilian authorities after nearly a year as to which procedures for lost communications actually applied at the time of the accident, how can anyone reasonably have expected two pilots on a delivery flight to know what those regulations may have been, other than those to which they were accustomed? And until that is determined, how could one even begin any kind of legal categorisation of the actions of the pilots or controllers? Yet, as I understand it, one criminal trial has formally begun already.
Second, you appear to be under the impression that when the Legacy pilots joined UZ6, they should have communicated with controllers about the heading change but didn't. I take it that marciovp's comment suffices to answer that.
Third, you ask me to define "lost communications". Communications are taken to be lost by one participant when they (repeatedly) attempt to communicate over the mutually established or conventional channel and do not succeed. A state of lost communications can only be established, as you say, when attempted but failed. The important point to note here, and which must be taken into account by IFR procedures for lost communications, is that one party will likely establish that communications are lost before the other.
Fourth, you say, concerning the FL at which the Legacy pilots flew UZ6, that
Originally Posted by Sdruvss
if you are in Brazil, as hundreds of pilots of Delta, AA, Fedex, United, Lufthansa, Air France, Air Portugal, Iberia, Alitalia, British Airways, …, it’s what they do each day
as if they "know" what is "right" and the Legacy pilots did it "wrong". Do you realise that you are conversing with some of these "hundreds" of pilots of established airlines in this forum? And that none of those whom I know personally have any idea at this point what it is that the Legacy crew are supposed to have done "wrong"?
As to your suggestion why the controllers are facing military tribunals,
Originally Posted by Sdruvss
Because Joe Lepore, Joe Sharkey, a lot of Brazilians and, a lot of foreigners are accusing them
you are, please, aware of the fact that the only people who seem to be taking a genuine interest and making a genuine effort to ensure that the inquiry into the behavior of these controllers proceeds appropriately are "a lot of foreigners", specifically, Swiss, French and Portuguese? With some of whom you are now conversing.
PBL