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Flight Reliability

UA 1821 · United Airlines

This number covered several routes in this period.

One number, several routes.

Airlines reuse flight numbers, and UA 1821 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

87%
Arrive within 15 minutes
0 min
Average arrival delay
1.8%
Cancelled
10 min early
Median arrival delay

Based on 623 historical flights. Data through May 2026.

The breakdown

On-time by weekday
  • Mon82%(93 flights)
  • Tue92%(87 flights)
  • Wed95%(85 flights)
  • Thu84%(86 flights)
  • Fri87%(90 flights)
  • Sat91%(77 flights)
  • Sun79%(92 flights)
On-time by departure window
  • 6–9 AM88%(257 flights)
  • 9 AM–12 PM96%(23 flights)
  • 12–3 PM91%(284 flights)
  • 6–9 PM52%(46 flights)
On-time trend by month
75%
May

Jun 80% → May 75% on time

On-time arrival percentage by month
MonthOn-time percentageFlights
June 202580%44
July 202597%30
August 202586%58
September 202593%60
October 202581%67
November 202576%80
December 202588%60
January 202694%64
February 202695%55
March 202691%35
April 202693%29
May 202675%28
Departures on time
90%
Diverted
0.3%
Flights flown
610
Months covered
12

Keep nerding

Based on 623 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.