The most avoidable travel disaster we see is the ticket bought on price alone, routed through a country whose transit rules the traveller never checked. Transit visas are the small print of the entire aviation system.
The core distinction: airside vs landside
Staying airside means remaining in the international zone without crossing immigration. Many countries allow visa-free airside transit for most nationalities. But any connection that requires collecting bags, changing terminals through immigration, or an overnight stay is landside — and landside means the full entry rules apply, visa and all.
The strict ones
- United States: no airside transit exists. Every connection through a US airport is an entry, requiring ESTA or a visa — even ninety minutes between planes to Mexico.
- Canada: similar logic; most transiting nationalities need an eTA or transit visa.
- United Kingdom: maintains a Direct Airside Transit Visa (DATV) list — some nationalities need a visa even to change planes without entering. Others need visas only to pass through the border.
- Schengen: a shorter airport-transit-visa list applies to certain nationalities; and remember an internal connection (Paris–Frankfurt–onwards) means you entered Schengen at the first airport.
How to check properly
Check by nationality, by airport, and by ticket structure — separate tickets usually force landside bag collection, converting an innocent airside connection into an entry. Airlines enforce all of this at check-in using the same databases we do, and they are unsentimental: no authorisation, no boarding, no refund on most fares.
When we book or check an itinerary, transit rules for every leg are part of the check. If you have bought a bargain routing and feel a flicker of doubt, that flicker is worth a five-minute question before it is a missed flight.