Delay causes by month, August 2024 to July 2026
Airlines gave 39.7% of the delay minutes to the BTS category "Late-arriving aircraft" in the 12 months to July 2026.
No other category had a larger share.
The next two categories were "Air carrier" (33.3%) and "National Aviation System" (20.7%).
The share of the BTS category "National Aviation System" ran from 18.0% in January 2026 to 26.7% in November 2025.
July 2026 had the most scheduled flights of the 12 months: 631,970.
A flight is considered on-time when it arrives less than 15 minutes after its published arrival time. This database contains scheduled and actual departure and arrival times reported by certified U.S. air carriers that account for at least half of one percent of domestic scheduled passenger revenues.
In plain words: a flight that arrives 14 minutes late is on time. A flight that arrives 15 minutes late is late. This site counts a cancelled flight and a diverted flight as not on time. The data holds domestic flights only.
Months, newest first
| Month | Flights | Arrived on time | Cancelled | Air carrier | Late-arriving aircraft | National Aviation System | Extreme weather | Security |
|---|---|---|---|---|---|---|---|---|
| July 2026 | 631,970 | 69.4% | 2.6% | 31.7% | 41.8% | 19.9% | 6.5% | 0.1% |
| June 2026 | 607,577 | 72.8% | 1.6% | 30.8% | 42.1% | 20.3% | 6.7% | 0.1% |
| May 2026 | 611,735 | 77.6% | 0.9% | 33.0% | 40.4% | 20.5% | 6.0% | 0.1% |
| April 2026 | 597,919 | 78.9% | 0.9% | 33.5% | 40.4% | 21.0% | 5.0% | 0.1% |
| March 2026 | 612,102 | 73.2% | 2.9% | 33.5% | 39.3% | 21.0% | 5.9% | 0.2% |
| February 2026 | 515,037 | 78.3% | 2.3% | 38.2% | 37.2% | 18.5% | 6.0% | 0.2% |
| January 2026 | 544,003 | 75.3% | 4.7% | 37.3% | 35.0% | 18.0% | 9.6% | 0.1% |
| December 2025 | 582,304 | 71.9% | 1.5% | 33.3% | 41.1% | 19.1% | 6.4% | 0.2% |
| November 2025 | 570,550 | 77.3% | 2.5% | 30.2% | 38.3% | 26.7% | 4.6% | 0.1% |
| October 2025 | 605,844 | 79.1% | 0.5% | 34.0% | 39.7% | 22.9% | 3.3% | 0.1% |
| September 2025 | 562,439 | 82.8% | 0.5% | 34.3% | 37.4% | 22.6% | 5.6% | 0.1% |
| August 2025 | 602,378 | 76.3% | 1.1% | 33.1% | 40.5% | 19.2% | 7.0% | 0.1% |
| July 2025 | 631,428 | 69.0% | 2.5% | 31.1% | 40.8% | 20.7% | 7.3% | 0.1% |
| June 2025 | 611,575 | 70.3% | 1.6% | 31.6% | 40.6% | 20.9% | 6.9% | 0.2% |
| May 2025 | 605,648 | 75.4% | 1.0% | 29.3% | 37.8% | 25.9% | 6.9% | 0.1% |
| April 2025 | 583,950 | 79.5% | 0.8% | 32.7% | 39.4% | 22.2% | 5.5% | 0.2% |
| March 2025 | 600,872 | 79.3% | 1.2% | 33.0% | 39.2% | 21.9% | 5.9% | 0.1% |
| February 2025 | 504,884 | 77.9% | 1.5% | 33.9% | 36.9% | 22.5% | 6.6% | 0.1% |
| January 2025 | 539,747 | 78.6% | 3.0% | 36.2% | 34.7% | 19.9% | 9.1% | 0.2% |
| December 2024 | 590,581 | 78.1% | 0.7% | 34.3% | 40.2% | 17.8% | 7.5% | 0.2% |
| November 2024 | 575,404 | 84.8% | 0.5% | 36.9% | 35.6% | 21.9% | 5.4% | 0.2% |
| October 2024 | 615,497 | 85.8% | 1.0% | 42.7% | 37.4% | 16.3% | 3.4% | 0.2% |
| September 2024 | 582,622 | 83.9% | 0.6% | 38.6% | 38.4% | 18.2% | 4.8% | 0.1% |
| August 2024 | 619,025 | 74.7% | 2.1% | 33.8% | 39.8% | 20.4% | 5.9% | 0.1% |
How the figures were made
Airlines assign the delay minutes of a flight to five BTS categories. The categories do not name a cause in the air or on the ground, and the table assigns no cause of its own.
The National Aviation System category includes weather that is not extreme, so the extreme weather share does not show all weather delay. See the guide to the delay-cause categories.
The sentences use the newest 12 of the 24 months in the table. The 12 months run from August 2025 to July 2026.
A program makes this page from the BTS files with fixed sentence rules. How the figures are made. BTS and TSA files.
In earlier editions
This table is in the edition of October 2026, the first edition. Each month adds an edition that keeps the first rows of the table as they were.