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Flight Reliability

UA 4257 · United Airlines

Washington → Knoxville (IAD–TYS)91% of its flights flew this route. The rest (ECP–IAH, IAH–CRP) are included in these numbers.

88
Pretty Reliable
WanderNerd Reliability Score
84%
Arrive within 15 minutes
4 min
Average arrival delay
0.8%
Cancelled
12 min early
Median arrival delay

Based on 369 historical flights. Data through May 2026.

What the data says

Mornings have a slight edge.

Departures between 6–9 AM arrived on time 87% of the time, against 82% between 9 AM–12 PM.

Friday is doing you no favors.

UA 4257 arrived on time 94% of the time on Saturdays and just 76% on Fridays. That gap is worth planning around.

A bit ahead of the IAD–TYS route.

UA 4257 arrived on time 84% of the time, versus 78% across the IAD–TYS route.

A bit ahead of the United Airlines network.

UA 4257 arrived on time 84% of the time, versus 79% across the United Airlines network.

The breakdown

On-time by weekday
  • Mon88%(50 flights)
  • Tue81%(53 flights)
  • Wed88%(50 flights)
  • Thu84%(50 flights)
  • Fri76%(53 flights)
  • Sat94%(54 flights)
  • Sun78%(55 flights)
On-time by departure window
  • 6–9 AM87%(162 flights)
  • 9 AM–12 PM82%(203 flights)
On-time trend by month
79%
May

Jun 87% → May 79% on time

On-time arrival percentage by month
MonthOn-time percentageFlights
June 202587%30
July 202594%31
August 202568%25
September 202586%29
October 202594%31
November 202596%28
December 202571%31
January 202679%28
February 202686%28
March 202674%31
April 202697%30
May 202679%43
Departures on time
85%
Diverted
0.3%
Flights flown
365
Months covered
12

Same route, other flights

Keep nerding

Based on 369 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.