The Player Dialog provides you with the ability to manipulate the AI players that are available, including disabled and enabled players.
To enable/disable a particular AI player you simply click on the checkbox(non-standard image). Please note though, that once disabled an AI's existing routes(if any) will continue to receieve revenue(or lose it), disabling an AI only 'puts them to sleep'.
The dialog also provides an overview of the current status of each competitor, giving you it's current bank balance, no other information is provided yet.