Many airlines find themselves at present in a transition period with regard to Engine Health Monitoring. The manual concepts used up to now are being replaced by computerized versions and almost parallel to this comes the introduction of the “On Condition Modular Maintenance.” The new High Bypass Engines (engines of the 3rd generation) along with the 2nd generation engines, were designed for “Modular Maintenance.” As a result, the efforts toward achieving an automatic engine performance control were also intensified. These new ideas of engine monitoring were repeatedly considered in determining the Modular Maintenance Concept.Both in the past and at present, airlines have to some extent applied very different engine trend monitoring methods, in theory and in practice. This shows that even good methods are not universally suitable.Swissair, which is completely autonomous on the one hand but which works in cooperation with the larger unit of KSSU, has specific problems in the exchange of information with regard to Engine Health Monitoring. We should like to explain the basis of Swissair's various Health Monitoring methods.