AreOut
10 If both engines fail over city, try to land in river if runway not available.
That software didn't seem too difficult to write!
Next!
In all seriousness, and no disrespect to Sullenberger who is an awesome pilot who made the correct decision with the knowledge that he had at the time.
'Miracle on the Hudson' Gets Closer Study, Finds Capt. Sully Sullenberger Could Have Landed at LaGuardia Airport - WSJ
This shows that a computer might have had another option. It would not have to guess, it would know whether it had the reach to get to the runway.