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hellogoodbye That image made me lose it. So many things wrong with it. "Journey of epic proportions"...yeah, that's one way to put it. "Wherever you go, no one will ever know" - that's for sure. To me the funniest part is that the pictured plane isn't actually a
Boeing 777 - it's an
Airbus A380.
With radar, though, it's somewhat complicated. There are two types of radar - "regular" radar that's been around since WWII that actually picks up "echos" bouncing off of objects (e.g. a plane), and "modern" radar that works together with equipment (i.e. the transponder) on board each aircraft. The aircraft originally disappeared off the newer radar system, so basically the transponder shut off. Military radar could still pick it up since it's of the older type, but the various countries that detected it on that radar didn't want to tell anyone because they didn't want the world to know how good their radar is. Slowly information is coming in from those countries, as well as info from the engines (transmitted via satellite). It all points to hijackers purposefully turning off various communications systems, then flying to points unknown.
In case you're wondering why "regular" radar couldn't track it all the way to wherever it is right now, it's either because the plane just got out of range, or they dropped below the minimum altitude radar can cover. Satellite imagery isn't any good because the area to be covered is
too large. Engines aren't pinging any more because by this point the plane has either landed and had those pieces shut off, or the plane has crashed and they were disabled that way. That's how a plane can disappear.