Abstract: An on-board aircraft telecommunication exchange (32) provides communication and authentication services for M subscriber identity modules (SIMs) using N transceivers (36), where M can be greater than N. Associations between SIMs (56) and transceivers (36) are established when needed. Accordingly, a pool of transceivers 36 is provided to serve the collective needs of many subscribers. A SIM-based authentication process is performed (100) using a subscriber's original SIM (56). That authentication can be extended to a temporary SIM (106) that is substituted for the original SIM throughout the remainder of a flight. Alternatively, the original SIMs (56) may be locked in place and relinquished when a subscriber provides an appropriate PIN.