Lawyers for Paul Chambers said Monday that leading human rights lawyer Ben Emmerson will lead the legal challenge to Chambers' conviction.
Chambers was arrested in January after he posted a message on Twitter saying he would blow Robin Hood Airport "sky high" if his flight was delayed.
Chambers insisted it was a joke. But a judge found him guilty of sending a menacing message over a public telecommunications network.
This month another judge rejected Chambers' appeal.
The verdict caused a wave of outrage on Twitter, with thousands of supporters retweeting Chambers' message.