Flight UA421
United Airlines flight UA421
Looking for UA421 in the airâŚ
Alerts at this flight's airports
-
Advisory Airport Closure SNA
Airport Closure at John Wayne Orange County International Airport (SNA): Reopens Nov 08 at 14:15 UTC.
Airport status
Santa Ana (SNA) to Denver (DEN)
Historically, this flight arrives 15+ minutes late 12% of the time, and when it is late the delay averages 75 minutes. It was cancelled 0.5% of the time.
- On-time arrivals
- 87.6%
- Less than 15 minutes late
- Cancelled
- 0.5%
- Of scheduled flights
- Average delay when late
- 75 min
- Flights arriving 15+ minutes late
- Flights tracked
- 187
- Scheduled flights in the period
What caused the delays
- Late-arriving aircraft 51%
- Air traffic control & airport 41%
- Airline (crew, maintenance, cleaning) 7%
- Extreme weather 0%
- Security 0%
Share of delay minutes airlines attributed to each cause (BTS).
Denver (DEN) to Milwaukee (MKE)
Historically, this flight arrives 15+ minutes late 15% of the time, and when it is late the delay averages 111 minutes. It was cancelled 0.0% of the time.
- On-time arrivals
- 84.5%
- Less than 15 minutes late
- Cancelled
- 0.0%
- Of scheduled flights
- Average delay when late
- 111 min
- Flights arriving 15+ minutes late
- Flights tracked
- 110
- Scheduled flights in the period
What caused the delays
- Airline (crew, maintenance, cleaning) 63%
- Late-arriving aircraft 26%
- Air traffic control & airport 11%
- Extreme weather 0%
- Security 0%
Share of delay minutes airlines attributed to each cause (BTS).
Denver (DEN) to Dulles (IAD)
Historically, this flight arrives 15+ minutes late 30% of the time, and when it is late the delay averages 57 minutes. It was cancelled 0.0% of the time.
- On-time arrivals
- 69.9%
- Less than 15 minutes late
- Cancelled
- 0.0%
- Of scheduled flights
- Average delay when late
- 57 min
- Flights arriving 15+ minutes late
- Flights tracked
- 103
- Scheduled flights in the period
What caused the delays
- Air traffic control & airport 52%
- Late-arriving aircraft 21%
- Airline (crew, maintenance, cleaning) 20%
- Extreme weather 7%
- Security 0%
Share of delay minutes airlines attributed to each cause (BTS).
Denver (DEN) to Louisville (SDF)
Historically, this flight arrives 15+ minutes late 29% of the time, and when it is late the delay averages 117 minutes. It was cancelled 0.0% of the time.
- On-time arrivals
- 70.8%
- Less than 15 minutes late
- Cancelled
- 0.0%
- Of scheduled flights
- Average delay when late
- 117 min
- Flights arriving 15+ minutes late
- Flights tracked
- 24
- Scheduled flights in the period
What caused the delays
- Late-arriving aircraft 69%
- Air traffic control & airport 22%
- Airline (crew, maintenance, cleaning) 9%
- Extreme weather 0%
- Security 0%
Share of delay minutes airlines attributed to each cause (BTS).
Dulles (IAD) to Chicago (ORD)
Historically, this flight arrives 15+ minutes late 33% of the time, and when it is late the delay averages 64 minutes. It was cancelled 0.0% of the time.
- On-time arrivals
- 66.7%
- Less than 15 minutes late
- Cancelled
- 0.0%
- Of scheduled flights
- Average delay when late
- 64 min
- Flights arriving 15+ minutes late
- Flights tracked
- 21
- Scheduled flights in the period
What caused the delays
- Airline (crew, maintenance, cleaning) 43%
- Late-arriving aircraft 39%
- Air traffic control & airport 16%
- Extreme weather 1%
- Security 0%
Share of delay minutes airlines attributed to each cause (BTS).
Salt Lake City (SLC) to Denver (DEN)
Only 19 flights on record, which is too few for reliable odds.
- On-time arrivals
- 63.2%
- Less than 15 minutes late
- Cancelled
- 0.0%
- Of scheduled flights
- Average delay when late
- 57 min
- Flights arriving 15+ minutes late
- Flights tracked
- 19
- Scheduled flights in the period
What caused the delays
- Late-arriving aircraft 51%
- Air traffic control & airport 29%
- Airline (crew, maintenance, cleaning) 19%
- Extreme weather 0%
- Security 0%
Share of delay minutes airlines attributed to each cause (BTS).
Los Angeles (LAX) to Phoenix (PHX)
Only 1 flight on record, which is too few for reliable odds.
- On-time arrivals
- 100.0%
- Less than 15 minutes late
- Cancelled
- 0.0%
- Of scheduled flights
- Average delay when late
- â
- Flights arriving 15+ minutes late
- Flights tracked
- 1
- Scheduled flights in the period
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Show as table
| Month | On time | Flights |
|---|---|---|
| September 2025 | 73.3% | 30 |
| October 2025 | 100.0% | 37 |
| November 2025 | 88.1% | 59 |
| December 2025 | 73.9% | 46 |
| January 2026 | 80.6% | 36 |
| February 2026 | 81.5% | 28 |
| March 2026 | 78.2% | 55 |
| April 2026 | 96.7% | 30 |
| May 2026 | 93.5% | 31 |
| June 2026 | 73.3% | 30 |
| July 2026 | 54.8% | 31 |
| August 2026 | 69.2% | 52 |
Source: U.S. DOT Bureau of Transportation Statistics on-time data, September 2025 â August 2026. Covers flights operated by reporting U.S. carriers. About our data