Texting takes off for pilots (11 Apr 2006)
Initial results suggest that it might be possible to reduce the amount of radio communication by relaying basic information such as aircraft altitude and heading as text.
But there are no plans to do away with radio communication all together. Several aircraft share a radio channel with a controller at any one time.
One advantage of everyone hearing everyone else's communication is that individual pilots build up a picture of where all the aircraft are in relation to each other. That would be hard to emulate through text-only communication.