When a booking site shows a 35-minute connection, it isn’t guessing — it’s selling you a layover that clears the airport’s minimum connection time (MCT). But MCT is a legal floor, not a comfortable buffer. The real question is how much margin you have above it.
What minimum connection time really means
Every airport publishes an MCT — the shortest gap an airline is allowed to sell between an arriving and a departing flight — and it differs for domestic vs. international connections, because international transfers can add immigration, customs, and a bag recheck. A booking engine won’t sell you a connection below MCT, but it will happily sell you one right at it. Land a few minutes late and that connection is gone.
What eats your buffer
- An inbound delay — the single biggest factor, and the one you can’t see when you book.
- Gate distance — a different terminal or concourse can be a 15–20 minute walk or a train ride.
- Immigration & customs on international arrivals, plus re-clearing security.
- Bag recheck if your luggage isn’t checked through.
- Deplaning — simply getting off a full widebody eats 10–15 minutes.
A practical rule of thumb
At a major hub, aim well above the legal minimum:
- Domestic: 60–90 minutes is comfortable; under ~45 is tight.
- International (or any customs): 90–120+ minutes.
- Add more for big/complex hubs, winter weather, or if it’s the last flight of the day — miss it and you’re overnighting.
Those are starting points, not answers. The right number for your connection depends on four things: how big and how spread out the hub is, whether you cross a border, what the weather is likely to be doing, and how bad it would be to miss the flight. Treat the numbers above as a baseline and then adjust deliberately.
See the real numbers
Adjusting the baseline for your actual connection
Add time for a big or awkward hub. A connection at a compact single-terminal airport is a genuinely different task from one that requires an inter-terminal train, a second security screening, and a fifteen-minute walk at the far end. Some large hubs are laid out so that most connections stay within one concourse; others routinely put arriving and departing gates a long way apart. If you don’t know the airport, assume the awkward version.
Add time for a border. Any itinerary that clears immigration and customs mid-trip needs materially more buffer, because you’re queueing behind an entire arriving widebody, then often reclaiming and rechecking a bag, then clearing security again. The queue length is the part you cannot predict — two flights landing together can double it.
Add time in winter, and in thunderstorm season. De-icing adds an unpredictable block of ground time to your inbound leg, and it’s applied on a queue. Summer convection can hold your inbound flight on the ground at the origin for an hour. Neither shows up anywhere in the connection time the booking site quotes you.
Add time if missing it is expensive. This is the one people skip. A missed connection on a Tuesday morning with six later flights on the same route is an inconvenience. The same miss on the last bank of the night, or before an onward international departure, or ahead of a cruise departure, is a hotel and a lost day. Size the buffer to the consequence, not just the odds.
You can subtract in a few genuine cases: a small airport where your arrival and departure gates are a two-minute walk apart, a same-aircraft “direct” flight where you never change planes, or a domestic connection early in the day when the inbound aircraft started its rotation at that airport. Just be sure the reason is real.
One ticket vs. two
If your whole trip is on a single ticket and you misconnect, the airline must rebook you on the next available flight at no charge. If you booked the legs as separate tickets to save money, a missed connection is entirely your problem — the second airline owes you nothing. That cheap self-transfer can become the most expensive part of the trip. If it does go wrong, here’s what to do the moment you misconnect.
The distinction matters more than almost anything else on this page, because it changes who absorbs the cost of a bad day. On one ticket, the airline owns the problem: rebooking, and in many cases meals and a hotel when the disruption was within its control. On two tickets you own all of it, and you will likely be buying a new one-way fare at same-day prices. It also affects your bags, which can only be checked through when the tickets are connected. The full picture is in the risk of separate tickets and self-transfers.
What the booking site isn’t telling you
A search engine sorts by price and total travel time, so a tight connection looks strictly better than a generous one: it’s cheaper and it gets you there sooner. Nothing in that ranking reflects the probability that the itinerary actually works. This is why the cheapest connecting option so often pairs the thinnest layover — you’re not being offered a bargain so much as being handed the risk.
The honest way to compare is to price in the failure. If a 45-minute connection saves you $60 over a 100-minute one, and the tight version fails often enough to cost you a hotel night and a rebooking even occasionally, the “cheap” itinerary is the expensive one on average. You don’t need precise numbers to make that call — you just need to stop treating layover length as dead time to be minimized.
The short version
Minimum connection time is a legal floor, not advice. Start at 60–90 minutes domestically and 90–120+ internationally, then add for hub complexity, borders, weather season, and the cost of missing it. Prefer one ticket. And when the fare difference between a tight connection and a comfortable one is small, buy the comfortable one — it’s the cheapest travel insurance available. For whether to connect at all, see nonstop vs. connecting flights.
Put it into practice
Score real flights on reliability, weather, and connection safety — not just price.