There is described a portable data transmission unit comprising a communications link for electrical connection to an aircraft engine to be maintained; an application coupled to a processor and configured for capturing in real time performance data indicative of a performance of the aircraft engine and making the performance data available for analysis upon landing of the aircraft, retrieving maintenance data related to the aircraft engine and performing maintenance operations on the aircraft engine; a user interface to display the maintenance data and receive input data, the maintenance operations performed on the aircraft engine directly through the data transmission unit using the input data and the maintenance data; a microphone to convert sound waves into an electric current; a speaker to convert analog audio signals into air vibrations to make audible sound; and a transceiver to transmit and receive in real time voice and data signals wirelessly across a network.