Systems and methods for establishing a push-to-talk (PTT) call are provided. When a group call request that identifies a first and second destination mobile station is received from an originating mobile station, a location of the first destination mobile station is determined. The call is established between the originating mobile station and the first destination mobile station prior to a determination of a location of the second destination mobile station. When the group call involves mobile stations of two different networks, a gateway of the second network sends an acknowledgement message accepting the call to a gateway of the first network and the gateway of the second network receives an acknowledgement message accepting the call from the first destination mobile station. The acknowledgement message is received from the first destination mobile station subsequent to the sending of the acknowledgement message from the second gateway to the first gateway.