For several years the aircraft industry has been looking for a technology to provide at a reasonable cost a phone service onboard aircraft. Nevertheless, some technical hitches make successful calls via the terrestrial Global System for Mobile Communications (GSM) network impossible. The mobiles unable to make reliable contact with ground-based base stations, would transmit with maximum RF power and these RF fields could potentially cause interference with the aircraft communications systems. On the other hand, the high speed of the aircraft causes frequent handover from cell to cell, and in extreme cases could even cause degradation of terrestrial services due to the large amount of control signalling required in managing these handovers. In order to avoid these problems and allow airline passengers to use their own mobile terminals during certain stages of flight, a novel approach called GSM On-Board (GSMOB) was suggested in 2005. The GSMOB system consists on a lowpower base station carried on board the aircraft itself, and an associated unit emitting radio noise in the GSM band, raising the noise floor above the signal level originated by ground base stations. Thus mobiles activated at cruising altitude do not see any terrestrial network signal, but only the aircraft-originated cell. This way, the power level needed is low, which reduces the interference with aircraft systems. This thesis provides a general overview on GSMOB system, which is nowadays being offered commercially by several relevant European airlines. Moreover, other aspects beyond the purely technical such as operational and regulatory issues have been addressed.