What to know about connections and layovers
A connection is two flights and the gap between them. The airline’s booking system decides whether the gap is long enough to sell. Whether it is long enough to make depends on how late the first flight lands that day. This guide sets out what each of those means and shows how often flights into the covered airports have landed too late for common layovers.
What a minimum connection time promises
A booking system will not sell an itinerary whose connection is shorter than the minimum connection time it holds for that airport. The minimum is a scheduling rule. It assumes the first flight arrives on time and the traveler moves at an ordinary pace, and it says nothing about how often the first flight is late. A connection at the minimum can be sold and still has no margin at all.
FlyerIntel does not publish minimum connection times and the DOT file does not contain them. It has flights, not itineraries. It cannot show whether two flights were sold on one ticket, and it has no gate or terminal information, so nothing in this guide says what an airline will accept or protect. What the file can show is how late the first flight has landed.
How a late arrival becomes a missed connection
The arrival delay of the first flight is measured at the gate: the time the aircraft reached it, against the scheduled time. Taxi-in is already inside that figure. Take the layover, subtract the time you need to leave the aircraft and reach the next gate, and what remains is the margin. The connection fails when the first flight is later than the margin. As an illustration, a 60-minute layover with 30 minutes needed leaves a margin of 30 minutes, and an arrival 31 minutes late misses.
The 15-minute line that decides whether a flight is “on time” (see the guide to how on-time performance is counted) does not apply here. A flight 14 minutes late is on time in every official statistic and has still used 14 minutes of the margin.
Delays also carry from one flight to the next. The first flight is often late because its own aircraft landed late from an earlier flight, which is why lateness builds through a day (see the delay causes guide and the research on what a late aircraft costs the next flight). The second flight can also leave late, which gives a late arrival extra time. The record used here measures only the inbound leg, so that effect is not in any figure below.
How often flights landed too late
The table gives the share of completed flights that landed later than each layover allowed, with 30 minutes needed after landing, grouped by the hour the flight was scheduled to arrive at the connecting airport. The last column is the layover that would have kept the chance of a miss to 1 in 20.
| Inbound flight due | Completed flights | 45 min layover | 60 min layover | 90 min layover | 120 min layover | 180 min layover | Layover for 1 in 20 |
|---|---|---|---|---|---|---|---|
| Any time | 17,543,441 | 20.7% | 13.7% | 7.5% | 4.7% | 2.1% | 116 min |
| 5–9 AM | 2,209,320 | 10.7% | 6.6% | 3.8% | 2.6% | 1.5% | 73 min |
| 9 AM–12 PM | 3,099,078 | 12.8% | 7.7% | 4.0% | 2.6% | 1.3% | 79 min |
| 12–3 PM | 2,969,393 | 16.7% | 10.5% | 5.5% | 3.4% | 1.6% | 96 min |
| 3–6 PM | 3,076,458 | 22.7% | 15.0% | 8.1% | 5.1% | 2.4% | 122 min |
| 6–9 PM | 3,149,978 | 28.6% | 19.6% | 11.0% | 6.8% | 3.0% | 142 min |
| 9 PM–5 AM | 2,812,795 | 30.6% | 21.3% | 11.8% | 7.0% | 2.8% | 142 min |
The hour matters as much as the length. At a 60-minute layover, 6.6% of flights due in the 5–9 AM window landed too late, against 19.6% of those due in the 6–9 PM window and 13.7% over the whole day. Keeping the risk to 1 in 20 took a layover of 73 minutes in the first window and 142 in the evening. The pattern is the build-up of delay through the day, seen on arrivals. The research on how long a layover needs to be gives the same measure for the busiest airports one by one, and found the evening needed the longer layover at every one of the 20 it measured.
These shares leave out flights that never reached the connection. Of the 17,857,944 flights scheduled on these routes, 268,821 were cancelled and 45,682 diverted, together 1.76%. A cancelled or diverted first flight ends a connection in a different way, and the guide to cancellation data covers how those are counted.
Reading the connection checker
The connection checker does the same arithmetic for one route. Enter where the first flight leaves from, the airport where you change planes, the layover in minutes, the hour the first flight is due and the time you need after landing. It offers 20, 30 or 45 minutes for the last, and 30 unless you change it. It returns how often flights on that route have landed too late for that layover, and the layover that would keep the chance to 1 in 20. For a flight that arrives at 6 PM, choose the evening window, because the whole-day figure hides the difference shown above.
The checker needs at least 750 flights on the route. If the arrival window you pick holds fewer than 120 completed flights, it falls back to the whole day and says so. Atlanta to Chicago with a 60-minute layover shows the layout.
Airports and the time you need
The time needed is the part the data cannot know. A terminal change, a train between concourses or a long taxi-in at a large airport takes more, and the difference comes straight off the margin. Taxi-in varies widely between airports, which the taxi time report sets out, and the report on the best airports for a tight connection ranks the covered airports on arrival delay and taxi-in.
What none of this covers
- Flights on one day share weather and air traffic control, so a bad afternoon raises the risk for every connection through an airport at once. The shares above are averages over many days, not a forecast for one.
- What an airline owes a traveler who misses a connection depends on the ticket and the airline’s own policy, which the data does not show. If a flight is cancelled, the refund checker works out whether a refund is owed.
- The glossary defines layover, scheduled arrival, time needed and the other terms used here.
What this is based on
The miss chances are counts of completed flights on 4,192 routes into the 64 covered airports, July 2023 – July 2026, read from each route’s arrival-delay distribution and added up before any share is taken. A route and arrival window counts only with at least 120 completed flights. They are history, and a single route can differ a great deal from the total.
- US Department of Transportation, 14 CFR Part 234, Airline Service Quality Performance Reports Sections 234.2 (definitions) and 234.4 (what carriers report, and the cause codes).
- Bureau of Transportation Statistics, Reporting Carrier On-Time Performance, field list The fields of the file FlyerIntel reads, including the 15-minute arrival indicator and the five delay-cause minutes.
An error in a figure or a definition can be reported on the corrections page. How FlyerIntel decides what to publish is set out in the editorial policy.
More guides
- How on-time performance is counted. The 15-minute rule, scheduled against actual times, and what happens to cancelled and diverted flights.
- Why flights are delayed: the five DOT causes. The five causes airlines report, what a late aircraft is, and where the delay minutes went.
- How to read an airport’s reliability profile. What each section of an airport page means, and how to compare airports without fooling yourself.
- Choosing a flight to avoid delays. Hour, day, airport, route and connection: what the record says to check, in order.
- How to read cancellation data. What counts as cancelled, the four cause codes, and how rates move by month and weekday.
- Glossary. Plain definitions of the terms the guides and the site use.