The Federal Communications Commission is in the process of allowing expanded use of phones in aircrafts, but the Department of Transportation plans to propose a rule this December that would prohibit making and receiving in-flight calls.
However, the DOT does not have any issue with texting or other data use, which would still free fliers up to do a lot more on their phones than they can right now.
The existing rules state that mobile phones must be switched-off when the aircraft sets to take off, in order to keep them from interfering with ground networks, but the FCC no longer believes in-flight interference is an issue.
In 2013, the FCC officially relaxed its restrictions on the use of portable electronics in flight, allowing them to be used during landing and takeoff while in Airplane Mode.
However, the use of electronics on flights has been quite limited until recently, and more options are still being opened up.
Once the FCC lifts limitations on cellphones, it'll be up to the individual airlines to determine their policies on usage of them.