How much time should I leave between connecting flights?

Booking systems will happily sell you a connection at the published minimum, and it will usually work. The problem is what happens on the day it does not, and that depends far more on the shape of the airport than on the number of minutes on the itinerary.

Step by step

1. Find out what kind of connection it is.Airside throughout at one terminal is the fastest. A terminal change by train or bus adds a lot. A connection requiring you to clear immigration, collect bags, re-check them and pass security again is a different exercise entirely and is the norm at several large hubs.
2. Account for what happens before you can start walking.Taxi time at a large hub can be lengthy, a remote stand means a bus, and disembarking a full wide-body from a rear seat takes a long time. None of this is under your control and all of it comes out of the interval.
3. Treat the gate closing time as the deadline.Gates close well before departure, and at many airports the gate is a long walk from the main concourse. The interval you actually have is shorter than the difference between the two flight times.
4. Double the published minimum for a through booking.It is calculated on everything running normally. Doubling it absorbs an ordinary late arrival and a longer than expected walk without drama, and on a through booking the airline carries the risk beyond that.
5. For separate tickets, allow for a whole delay.The gap has to be long enough to survive the first flight being late, because nobody will rebook you. Several hours is a working minimum, and an overnight is safer still on a long or important journey.
6. Check the bag position explicitly.Ask whether bags are checked through to the final destination. If they are not, add the reclaim time, the re-check time and the queue, and remember that a checked bag on a separate ticket cannot be checked in before the second airline opens its desk.
7. Prefer the outbound risk over the inbound one where you can.A missed connection on the way out costs you holiday. A missed connection on the way home costs you a day of work and a new ticket. Build the return connection longer.

Tips

• The first flight of the day is the least likely to be delayed, because the aircraft has not had time to accumulate a problem. Where a tight connection is unavoidable, book the earliest bank of flights.
• Some airports publish separate minimum connecting times for domestic-to-international, international-to-domestic and terminal changes. Find the one that matches your actual movement.
• If you have reduced mobility or are travelling with young children, book assistance and add time. Assistance is reliable but it is not fast.

Common mistakes

• Booking the minimum because the system offered it — Booking engines sell to the published minimum. That figure exists to define liability, not to give you a comfortable transfer.
• Ignoring a terminal change — At large hubs a terminal change can involve a train, a walk and a second security screening, and it routinely takes longer than the whole airside walk at a smaller airport.

Questions people ask