July vs. October Flight Reliability: What Four Years of U.S. Airline Data Show

How Often Did July and October Flights Arrive Within One Hour?

In July, 86.59% of the 2,630,641 operations reached their destination within 60 minutes of schedule. In October, 94.62% of the 2,555,475 operations did. The unadjusted difference was 8.03 percentage points. Flights arriving more than 60 minutes late, cancellations, and diversions that did not reach the destination in time counted as deadline failures.

The gap appeared in all four years, but varied from 4.86 to 10.25 percentage points. Combined results weight each flight equally rather than averaging annual percentages. July and October were selected after examining the monthly data, so this is an exploratory comparison, not a prespecified seasonal test.

Did Different Routes and Airlines Explain the Difference?

A national average can change when the mix of flights changes. We therefore compared July and October within the same calendar year, first by origin–destination airport pair, then by route and operating airline, and finally by those factors plus the scheduled destination arrival time grouped into six-hour periods.

At the most detailed level, the comparison included 53,420 year-specific flight groups, with at least ten known outcomes in each month. Those groups contained 2,175,919 July operations and 2,149,994 October operations. Both months were weighted within each group using the smaller of their two operation counts. The standardized success rates were 86.65% in July and 94.78% in October.

The October advantage also remained positive after detailed matching in each year: 4.96 points in 2022, 8.91 in 2023, 10.55 in 2024, and 7.82 in 2025. The matched groups contain comparable flights, not the same flight-number instances. Matching cannot establish that the month itself caused the difference.

Did the Minimum Group Size Change the Result?

The primary matched analysis required ten known flights in each month for a group to count. Repeating the comparison with different cutoffs produced:

The differences were similar with cutoffs of one, ten, and 25 flights. The 50-flight cutoff covers only about one-third of flights, so its larger difference describes a much narrower group and should not replace the primary result.

How Much Did Cancellations Contribute?

There were 64,530 cancellations in July across the four years, or 2.45% of scheduled operations. October recorded 17,075 cancellations, or 0.67%. The difference in cancellation rates was 1.78 percentage points, approximately 22% of the unadjusted 8.03-point difference in deadline success.

The remaining 6.24 percentage points correspond arithmetically to differences in other failures, such as arrivals more than an hour late or diversions that did not reach the scheduled destination in time. This calculation does not establish why those events occurred.

What Does This Comparison Mean for Flight Planning?

The results show that reliability varies across travel periods. They do not establish that moving an individual trip from July to October would increase its success probability by eight percentage points, or that any particular flight will arrive by its deadline.

If you are choosing between two to eight U.S. domestic nonstop flights on the same route, compare your flights using your own airport-arrival deadline. MakeItBy estimates historical deadline reliability for the submitted flights; it is not a live forecast of weather or disruptions. Planning for a cruise? Calculate the latest acceptable airport arrival before comparing flights.

For details on how MakeItBy's predictive estimates were tested separately, see Historical Testing. The figures on this page are descriptive BTS observations, not validation metrics for MakeItBy's model.

Methods, Sources, and Limitations

Data: U.S. Bureau of Transportation Statistics (BTS), Marketing Carrier On-Time Performance. The source reports scheduled U.S. domestic nonstop operations in the reporting airline networks. It includes regional code-share partners; it should not be interpreted as every flight operated nationally.

Arrival outcome: Success means reaching the scheduled destination gate no more than 60 minutes after the published scheduled arrival time. Ordinary flights use BTS ArrDelay. Diversions that later reach the original destination use the corresponding diversion arrival delay; cancellations and diversions that never reach the scheduled destination are known failures. The eight months in this comparison have no unresolved outcomes.

The standard BTS on-time statistic instead means reaching the gate less than 15 minutes after schedule; see the BTS 2025 On-Time Reporting Directive. This article's 60-minute rates are independently calculated and are not official BTS on-time percentages.

Methods: We used July and October of 2022–2025 (5,186,116 scheduled operations), verified the source month and operating-flight identifiers, and checked the resulting counts against monthly totals. The overlap comparison matches year, directed airport pair, operating airline, and four six-hour bins of scheduled destination-local arrival time. Groups with at least ten known outcomes in each month were retained. Within each group, the two months receive the same weight: the smaller observed month count. The reported standardized difference is calculated from those weighted group rates.

Limits: July and October were selected after reviewing monthly patterns. Only four July–October year pairs were observed. The matching does not control flight number, exact arrival hour, weekday mix, aircraft, weather, or airport-specific conditions on the travel date. It is not a causal estimate or a forecast for future seasons. The broader January 2022–June 2026 BTS archive audit covered 33,432,890 source records with one documented August 2024 exclusion and four unknown outcomes. That excluded record is outside this article's eight-month comparison.

Source Documentation: BTS Dataset Description and BTS 2025 Reporting Instructions. Analysis completed October 2026.