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Flight Reliability

UA 5566 · United Airlines

San Francisco → Sacramento (SFO–SMF)96% of its flights flew this route. The rest (MKE–ORD, TVC–ORD) are included in these numbers.

79
Usually Fine
WanderNerd Reliability Score
79%
Arrive within 15 minutes
16 min
Average arrival delay
0.7%
Cancelled
2 min early
Median arrival delay

Based on 298 historical flights. Data through May 2026.

What the data says

The late departure is the smart one here.

UA 5566 departing between 6–9 PM arrived on time 83% of the time, versus 58% between 6–9 AM.

Sunday scaries are real for this one.

UA 5566 arrived on time 97% of the time on Tuesdays and just 69% on Sundays. That gap is worth planning around.

Slipping a little lately.

UA 5566 arrived on time 77% of the time over the last three months in the data, compared with 82% in the three months before that.

The breakdown

On-time by weekday
  • Mon77%(47 flights)
  • Tue97%(33 flights)
  • Wed75%(40 flights)
  • Thu83%(46 flights)
  • Fri77%(47 flights)
  • Sat78%(37 flights)
  • Sun69%(45 flights)
On-time by departure window
  • 6–9 AM58%(12 flights)
  • 6–9 PM83%(35 flights)
  • 9 PM–12 AM79%(248 flights)
On-time trend by month
52%
May

Jun 83% → May 52% on time

On-time arrival percentage by month
MonthOn-time percentageFlights
June 202583%30
July 202567%30
August 202585%26
September 202582%17
November 202582%28
December 202579%28
January 202683%23
February 202684%25
March 202695%20
April 202683%30
May 202652%31
Departures on time
82%
Diverted
0.3%
Flights flown
295
Months covered
12

Same route, other flights

Keep nerding

Based on 298 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.