A risk assessment guideline for infectious diseases transmitted on aircrafts has been developed by the European Centre for Disease Prevention and Control (ECDC) [8] , which includes influenza. Literature study revealed on-board transmission in flights with a duration of less than 8 h. The majority of infected contacts during these flights were seated on the same row, or one or two rows in front of behind the index [9] [10] [11] [12] . Contacts up to 8 and 10 rows distance from the index were infected in one study [10] . As these contacts also had personal contact with the index during the flight, transmission across a distance of so many rows is not proven. The guideline concludes that it is difficult to design a single contact tracing algorithm for influenza. Due to the short incubation period of influenza, it is almost impossible to provide contacts with postexposure prophylaxis (PEP) within the time that it is most effective, which is 48 h after exposure [13] . Therefore, the main aim of contact tracing might be to interrupt the chain of transmission by alerting contacts for early diagnosis and treatment. Although the World Health Organization (WHO) developed technical advice for case management of influenza A/H1N1 2009 in air transport during the pandemic [14] , no international standardized protocol for contact tracing for this pathogen was available.