Which months have the most flight delays?

In July 2026, 28.3% of U.S. flights arrived 15 or more minutes late, the most of the 12 months from August 2025, when summer thunderstorms meet full planes. September 2025 was the best month, at 16.6%. Each bar is one month of the latest year of data, not an average over many years.

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Key facts

Measure: % of flights arriving 15+ minutes late. Written from the data below.

  • Jul 2026 has the highest figure, 28.3%, followed by Dec 2025 (26.8%) and Jun 2026 (25.7%).
  • Sep 2025 has the lowest figure, 16.6%, followed by Feb 2026 (19.8%) and Apr 2026 (20.2%).
  • The highest is 1.7 times the lowest.

Source and date

Source
U.S. Bureau of Transportation Statistics, Airline On-Time Performance (Reporting Carrier On-Time Performance, 1987–present)
License
Public domain (U.S. government work)
Data as of
Published

Citation

Chartly. “Which months have the 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/flight-delays-by-month (accessed October 15, 2026).

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The data

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Month % of flights arriving 15+ minutes late
Aug 2025 22.6
Sep 2025 16.6
Oct 2025 20.3
Nov 2025 20.6
Dec 2025 26.8
Jan 2026 20.8
Feb 2026 19.8
Mar 2026 24.3
Apr 2026 20.2
May 2026 21.4
Jun 2026 25.7
Jul 2026 28.3

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