TiberiusKirk said:
While it is indeed possible to extend radar coverage to every part of the globe...
Not with ground/land based radar it isn't. Radar is line of sight and the earth is curved. Even at altitude, an aircraft will often be below the horizon WRT to the nearest land.
Not true. Radar at microwave frequencies (1GHz+) is line of sight limited, but at HF (3-30MHz) propagation is either via refraction in the ionosphere to ranges between 500 and 3500 km (HF Over the Horizon Radar) or typically 0-500km when vertically polarised and over the sea (HF Surface Wave Radar). Thus it is indeed possible to extend coverage to every part of the globe, just not with the typical L-Band or S-Band ground based radars that you are probably familiar with. Several countries have operated or continue to operate HF OTHR systems, although none (as far as I am aware) are providing surveillance over the region of this crash.
Later edit: JDDE you
replied to the above message disputing HF Surface Wave Radar and telling me to learn more about antennas and propagation. I replied to your reply, but this was deleted by the mods. Suffice it to say that I have been a radar engineer for almost 20 years and worked extensively on both of the above technologies. Your comments on NVIS are nothing to do with the technologies I am referring to.