What's the Worst Month to Fly? Delays by Season
By Sharon Ben-Moshe ·
July is the worst month to fly for delays — only about 70% of flights arrive on time — with June close behind. The best stretch is fall: September through November all run about 82–84%. The pattern is steady across 14.1 million US flights from June 2024 through May 2026 from the US DOT.
Delays are worst in summer
Thunderstorms, peak vacation volume, and packed schedules make June and July the roughest months, with on-time rates in the low 70s. August recovers somewhat.
Cancellations peak in winter
Delays and cancellations don't peak together. Cancellations are highest in January (about 3.9% of flights) due to snow and ice, even though January's on-time rate is middling. If avoiding a cancellation matters most, deep winter is the riskiest time.
The best months to fly
- September — about 84% on time, the best month
- October and November — around 82–83%
- Spring (April) — solid, in the high 70s to low 80s
Check the monthly on-time reports for the latest month, and pair this with the best day of the week to fly.
Frequently asked questions
What is the single worst month to fly?
July, with on-time rates around 70% — the lowest of the year — driven by summer storms and heavy travel volume.
When is the best time of year to fly?
Early fall. September has the best on-time rate of any month, followed by October and November, before winter weather arrives.