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Flight Reliability

UA 4239 · United Airlines

This number covered several routes in this period.

One number, several routes.

Airlines reuse flight numbers, and UA 4239 moved between routes during this period. Numbers below combine all of them, so treat them as background, not a verdict. For a cleaner answer, check the route you are actually flying.

Combined across all its routes

83%
Arrive within 15 minutes
10 min
Average arrival delay
2.8%
Cancelled
7 min early
Median arrival delay

Based on 318 historical flights. Data through May 2026.

The breakdown

On-time by weekday
  • Mon80%(45 flights)
  • Tue80%(40 flights)
  • Wed86%(44 flights)
  • Thu84%(50 flights)
  • Fri77%(47 flights)
  • Sat87%(39 flights)
  • Sun88%(42 flights)
On-time by departure window
  • 6–9 AM89%(44 flights)
  • 9 AM–12 PM91%(58 flights)
  • 12–3 PM77%(175 flights)
  • 3–6 PM—(2 flights)
  • 9 PM–12 AM96%(28 flights)
On-time trend by month
77%
May

Jun 68% → May 77% on time

On-time arrival percentage by month
MonthOn-time percentageFlights
June 202568%28
July 202576%29
August 202586%22
October 202592%26
November 202590%19
December 202562%29
January 202693%27
February 202686%28
March 202690%31
April 202693%29
May 202677%31
Departures on time
86%
Diverted
0.6%
Flights flown
307
Months covered
12

Keep nerding

Based on 318 historical flights, because apparently we checked. Historical flight data: U.S. Bureau of Transportation Statistics, June 2025 – May 2026. Data through May 2026. How we calculate this.