Fink,
I believe the plane incident occurred at night. Had the plane crashed on land, it is very possible that one of the numerous satellites (U.S., Russia, China) would have spotted a red flash. I'm certain they were tasked with looking for such. Crashing a plane straight into the ocean would unlikely result in a red fire ball. It would leave debris, but remember that each part of it is traveling at the same rate of speed. It would likely submerge before dispersing into a debris field. TWA 800, if I recall, was a mid-air conflagartion that occurred immediately and ripped the plane apart. That scenario, based on what we have been told, isn't close to being applicable to this flight. Of course what we have been told may be subject to accuracy.