IIRC when the other Malaysian Airlines plane went missing that went up on HN, and that was before all the 'hacker friendly' tracking technique stories.
A modern airliner (seemingly) disappearing without a trace is interesting, even from a technology perspective.
A modern airliner getting shot down by a SAM is fairly boring from a tech perspective. Sadly it's not even a particularly unique occurence over the past few decades.
People are unfortunately probably going to post stuff like this, guidelines or not. It gets flagged and or moderated down pretty quickly in most cases, though.
Why unfortunately? In such cases, HN usually provides a lot of insightful technical comments. If a mainstream news item considers technology or failures thereof, I don't see why it doesn't belong on HN.