In the period April 29th until June 22nd 2009, 24 indications for CT were identified. Three international requests concerning CT for influenza patients diagnosed outside the Netherlands were declined as already more than 4 days had elapsed since flight arrival. In 17 out of the 21 remaining contact investigations, passenger lists with contact details were obtained within 7 days after arrival (81%), see Table 1 . In total contact details of 451 close contacts were identified, of which 199 contacts lived in the Netherlands, and 252 contacts abroad. The average number of close contacts per flight was 27 (range: 8-44). In four contact investigations (19%), contact details were not obtained, or provided later than 7 days after flight arrival and CT was stopped. These CT were all related to non-Dutch airlines, and total delay *:. In the beginning of the pandemic one request for contact tracing was accepted after 7 days **: these late CT requests were accepted as the passenger lists of the concerned flights already were available from earlier contact investigations ***: date of diagnosis not known ª: Passenger Locator Card was stated 8 days for further data processing. Of the 21 requests, the total delay between request and contact detail identification was longer for non-Dutch airlines (mean 6,3 SD 2,7) compared with Dutch airlines (mean 4.1 days, SD 1,5)(1-sided Mann-Whitney test, p = 0,033).