What causes most flight delays?
From August 2025 to July 2026, 39.7% of all minutes of delay came from a late-arriving aircraft: a plane that left its last airport late. The airline itself (crew, maintenance, cleaning, fueling) caused 33.3%, the air traffic system 20.7% and severe weather 6.1%. Weather also hides in the other causes: BTS counts ordinary weather that slows traffic under the air traffic system.
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Key facts
Measure: % of all minutes of delay. Written from the data below.
- Late-arriving aircraft has the highest figure, 39.7%.
- Security has the lowest figure, 0.1%.
- The highest is 397 times the lowest.
Source and date
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- Published
Citation
Chartly. “What causes most flight delays?” Chart. Data: U.S. Bureau of Transportation Statistics, Airline On-Time Performance (Reporting Carrier On-Time Performance, 1987–present), https://www.transtats.bts.gov/DL_SelectFields.aspx?gnoyr_VQ=FGJ&QO_fu146_anzr=b0-gvzr (data as of July 31, 2026). https://chart.ly/charts/causes-of-flight-delays (accessed October 15, 2026).
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The data
Download data (CSV)The file has the numbers in this table, with the source, license and date. Please credit the source and Chartly.
| Cause of delay | % of all minutes of delay |
|---|---|
| Late-arriving aircraft | 39.7 |
| The airline (crew, maintenance, cleaning, fueling) | 33.3 |
| Air traffic system (congestion, airport, ordinary weather) | 20.7 |
| Severe weather | 6.1 |
| Security | 0.1 |
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