Island in the Sky

The main character has spent 20 years in prison deep within the earth and in the mean time war had come and then the Airmen took control to rebuild and prevent further conflict. The survivors of the war have been gathered into cities that are isolated and controlled by a ruling class of Airmen. The ex-prisoner sees the space platform where most of the Airmen live and control those on earth and he decides to get up there and fight for freedom. In the mean time he is seized by a press gang and becomes a gladiator for the games used to distract the oppressed city dwellers.