A method for processing Aircraft Communications Addressing and Reporting System (ACARS) messages at a Communications Management Unit (CMU) on an aircraft is provided. The method includes, for an ACARS downlink message, receiving a message at the CMU from an application on a computer external to the CMU onboard the aircraft, reading a field in the message that indicates a message type for that application, determining an ACARS label associated with the message type, using the determined ACARS label instead of the industry standard ACARS label/sublabel associated with the onboard application external to the CMU, and sending the ACARS downlink message encoded with the determined ACARS label to a ground system to be delivered to a peer ground application.