An important issue at the start of the H1N1/2009 pandemic is global reporting of pandemic cases. Reports during the first few weeks of the pandemic showed spread of the disease from Mexico to many countries, but few cases were reported from low and middle income countries. Analysis of the data of international passengers departing from Mexican airports early in the H1N1/2009 outbreak shows a strong association between the number of passengers and reports of confirmed cases. In developing countries first case detection was slower and the chance of reporting the influenza cases after controlling for air traveller intensity was significantly lower. Delays in detection and reporting can jeopardize the success of a global response to a pandemic. A number of implications can be drawn from this, including the need to strengthen health system surveillance capacities in developing countries in Southeast Asia and globally for a better regional and global response.