Wow! Lots of headlines there! I wish I had time tonight to read them all.
I read the 990 report though. This "Hawkeye" doesn't identify his sources, so I'm more than a little skeptical, but I can answer his question about what happened to everyone on board. When things hit the water as fast as 990 did, they tend to disintegrate into unidentifiable pieces. Organic material, such as the occupants of airplanes, wind up doing their part for the food chain, and after passing through a fish's digestive tract, wind up as silt on the ocean floor.
Still, I wouldn't put anything past any government, not just the US. Let me know if you find unrelated sites that corroborate Hawkeye's story. It would be interesting to assimilate the information from independent sources and see what comes up.