So you may well ask why this is "not subject for a briefing"
The answer is that other NOTAM were issued for the event which were mandatory and were marked for inclusion in briefings (B in place of M in the purpose field). The old AIS site allowed you to choose "GENERAL" OR "GENERAL + MISC" to exclude miscellaneous NOTAM if you wanted to. Wisely the new site doesn't give you the option and includes them. Other briefing services may work differently.
Mike,
You seem to misunderstand the criteria for deciding if the NOTAM is goignt o be N, B, O or M.
The NOTAMS you display clearly show the true reason for two being M (not operationally significant and not automatically included in briefings) and two being NBO (operationally significant and included in briefings).
You will note that in the two "M" cases they are simply letting other users of class G airspace know that in a certain portion of that airspace there will be other users doing x,y,z but those users have no exclusive right regarding the airspace and while you are being made aware of their presence, you are not
required to avoid the airspace and can simply operate in that airspace on a see and be seen basis just as you do in the rest of Class G. If you decide to avoid the airspace, use an ATS service etc etc is totally up to you.
The the case of the two "NBO" NOTAMS there is a case of restricted airapce and one must comply with the restriction. There is not the option to fly as normal in class G and consequently this restriction is more than simply good to know information - it is essential and operationally significant.
One could aregue that parachuting is operationally significant but ICAO do not think so because in the case of parachuting operations, they say that there should be other safeguards to the operation before it gets approval - something that the CAA seems to forget!!
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So in response to the initial post - yes you missed the NOTAM and it could have been a safety issue. In this case it was not. However, remember that things like notamplot do not display all the applicable notams and in order to get a full briefing you have to a) read all the plotted ones and then b) read all the unplotted ones - which makes for more reading than a simple narrow route briefing from AIS.
If you learn how to quickly and accurately define a route in the AIS briefing and use a sensible corridor width then you will find that the number of notams will be greatly reduced.
Regards,
DFC