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(UA) United Airlines 4521 On-Time Performance Rating

Date Range:

15-Jul-2026 to 15-Sep-2026

(BUF) Buffalo Niagara International Airport

Buffalo, NY, US

(IAD) Washington Dulles International Airport

Dulles, VA, US

On-Time Performance Chart

(using rounded numbers)
On-Time
3
75%
Late
0
0%
Very Late
0
0%
Excessive
1
25%
Cancelled
0
0%
Diverted
0
0%

Delay Statistics

(Aggregate Arrival Delay Statistics for this Flight)

Total Flights Observed
4
Total Delays ( > 1 min )
2
Codeshares
4
Average Delay (min.)
88
Standard Deviation
111.7
Min
0
Max
167

UA 4521 On-Time Performance Details

Overall Rating
1.6 of 5
Average
Percentage On-Time 75%
Average Delay Time 88 min
FlightStats Rating is a merit measurement considering both on-time performance and delay severity. The score, 1.6 shows that this flight has on-time performance characteristics better than 31% of all other flights in the FlightStats database.
On-Time Performance Rating
2.7 of 5
Average
Percentage On-Time 75%
This flight has an on-time performance of 75%. Statistically, when taking into consideration sample size, standard deviation, and mean, this flight is on-time more often than 54% of other flights.
Delay Performance
0.5 of 5
Very Poor
Average Delay Time 88 min
This flight has an average delay of 88 minutes with a standard deviation of 111.7 minutes. Statistically, when taking into consideration sample size, standard deviation, and mean, this flight has delay performance characteristics better than 10% of other flights.

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