On the basis of findings from recent surveys, discussion has been raised as to whether the annoyance of residents at a given aircraft noise exposure level has increased over the years. To verify the hypothesized trend and to identify its possible causes, the large database used to establish earlier exposure-response relationships was updated with original data from several recent cross-sectional surveys. On the basis of these original data, it was investigated whether characteristics of the study can explain the heterogeneity between airports. A significant increase over the years was observed in annoyance at a given level of aircraft noise exposure. Furthermore, the type of annoyance scale used, the type of contact with respondents and the response percentage were found to be sources of heterogeneity. Of these only the scale factor could statistically account for the year effect, but other research findings seem to rule this out as a satisfactory explanation. Other possible explanations for the year effect, such as the higher rate of expansion of airports in recent years or changes in acoustical characteristics, could neither be confirmed nor ruled out. The results will be discussed in the light of recent findings from the ANASE study and the HYENA study, and the implications for exposure-response relationships for aircraft noise annoyance.