This might be old news.
There are any number of automated communications between airliners and various ground agencies. They use a variety of channels, with some redundancy. Those were working as intended. That plane just seemed to disappear with no warning of impending problems.
And there are other interesting things. A friend of mine watched with more than normal interest when that plane went into the Hudson. She designs small turbines which ride in the back of commercial airplanes. When the power goes out, as it did when birds took out both engines, it swings out into the slipstream and generates power for essential electrical systems.
She said that on that Continental plane it worked perfectly. I would have never known there was such a thing.