Exploring the Use of Aggregate Air Passenger Data for Estimating Overstayer Inflows

Overstayers —individuals entering a country with a valid visa but staying beyond the initially authorized period—are a blind spot of migration research. Past studies claim that overstaying is indeed the main gateway to irregular migration in Europe, but few estimates exist. This paper explores a new method to estimate the inflows of overstayers arriving via airline travel. We concentrate on the Schengen area as destination and on non-European countries as origins since commercial flights are the most likely transportation mode to Europe for travellers from these countries. Our method relies on aggregate information on incoming and departing passengers from all airports in the Schengen Area. First, we compute ‘net air travel flows’ as the difference between incoming and outgoing passengers. Second, we subtract regular flows. We rely on net migration figures from the QuantMig project to produce an estimate of overstay inflows through air travel in the year 2019, disaggregated by region of origin. The briefing discusses initial findings, advantages and limitation of this this approach.