Welp, since I'm a pilot, and have experienced some of these things, I'll toss the following out for your reading enjoyment
Transponders are pretty cool. A plane turns it on and you can be seen on ATC radar. However, they are line of sight, the signal does not follow the curvature of the earth. Transponders can also be turned off in the cockpit.
ELT's (Emergency Locator Transmitters) are also pretty cool, and most every plane has to carry one. They activate on an impact, or should. Limited battery life, on the order of 24-48 hours. Though Big Iron ELT's may stay live longer? They too can be turn off, though it's somewhat of a chore (remove the batteries). Probably more of a chore in Big Iron (like a 777)
If I have the facts right, the plane was flying at night. Satellite photography would be kinda useless, even if the satellite had IR capabilities. Aside from the many boats down there, how would you identify a target, triangulate the course, and track it to contact with earth? And last I knew, the NSA does not have radar satellites up there, though they wouldn't tell me if they did. Morons
777's have a monster range, assuming they have full tanks. Big Iron carries enough fuel to get to their destination, with a modicum of reserve. Not a drop more, flying extra weight costs the airlines big bux.
The engine monitor 'pings' are interesting. They should shut down on impact. And they probably only 'ping' one particular satellite with their data, no way to triangulate position.
Passengers cell phones could be triangulated, if there were any cell towers near by.
Small Cessnas and Pipers fly across the Atlantic (no joke), and have to carry LF radios with them (think Marconi). Even so, they often loose contact with ATC, and have to call big planes above them to relay position reports to ATC. They are basically flying across the Atlantic with a compass and/or GPS.
As far as a rogue plane entering USA airspace, we have this thing called ADIZ. It's a 'line' that is basically aligned with the international waters border with USA waters (it's actually closer to USA in *many* locations). Basically. If you don't have a flight plan ON FILE, and be in contact with ATC before you cross this line, some mid level manager with a bad comb over will scramble F-18's and stuff. Now think how fast this mid level manager would have to react if a plane (say a 777?) crossed this line at 580MPH
I'm thinking aliens.
Rick