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Flight Reliability

UA 4423 · United Airlines

St. Louis → Chicago (STL–ORD)86% of its flights flew this route. The rest (ORD–CHA, ORD–MSN) are included in these numbers.

87
Pretty Reliable
WanderNerd Reliability Score
85%
Arrive within 15 minutes
6 min
Average arrival delay
0.5%
Cancelled
8 min early
Median arrival delay

Based on 385 historical flights. Data through May 2026.

What the data says

The 6–9 AM departure wins.

UA 4423 departing between 6–9 AM arrived on time 86% of the time, versus 76% between 9 AM–12 PM.

Sunday scaries are real for this one.

UA 4423 arrived on time 93% of the time on Saturdays and just 73% on Sundays. That gap is worth planning around.

Better than the STL–ORD route average.

UA 4423 arrived on time 85% of the time, versus 72% across the STL–ORD route.

A bit ahead of the United Airlines network.

UA 4423 arrived on time 85% of the time, versus 79% across the United Airlines network.

The breakdown

On-time by weekday
  • Mon79%(56 flights)
  • Tue85%(54 flights)
  • Wed91%(55 flights)
  • Thu89%(52 flights)
  • Fri85%(53 flights)
  • Sat93%(54 flights)
  • Sun73%(55 flights)
On-time by departure window
  • 6–9 AM86%(329 flights)
  • 9 AM–12 PM76%(50 flights)
On-time trend by month
94%
May

Jun 91% → May 94% on time

On-time arrival percentage by month
MonthOn-time percentageFlights
June 202591%55
July 202577%30
August 202584%31
September 202597%30
October 2025100%31
November 202586%29
December 202580%30
January 202675%28
February 202682%28
March 202676%29
April 202667%27
May 202694%31
Departures on time
86%
Diverted
1.0%
Flights flown
379
Months covered
12

Same route, other flights

Keep nerding

Based on 385 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.