Flight UA1521
United Airlines flight UA1521
Looking for UA1521 in the airâŚ
Alerts at this flight's airports
Denver (DEN) to Cleveland (CLE)
Historically, this flight arrives 15+ minutes late 13% of the time, and when it is late the delay averages 65 minutes. It was cancelled 0.0% of the time.
- On-time arrivals
- 86.6%
- Less than 15 minutes late
- Cancelled
- 0.0%
- Of scheduled flights
- Average delay when late
- 65 min
- Flights arriving 15+ minutes late
- Flights tracked
- 186
- Scheduled flights in the period
What caused the delays
- Late-arriving aircraft 73%
- Airline (crew, maintenance, cleaning) 19%
- Air traffic control & airport 9%
- Extreme weather 0%
- Security 0%
Share of delay minutes airlines attributed to each cause (BTS).
Des Moines (DSM) to Denver (DEN)
Historically, this flight arrives 15+ minutes late 17% of the time, and when it is late the delay averages 84 minutes. It was cancelled 1.0% of the time.
- On-time arrivals
- 83.3%
- Less than 15 minutes late
- Cancelled
- 1.0%
- Of scheduled flights
- Average delay when late
- 84 min
- Flights arriving 15+ minutes late
- Flights tracked
- 103
- Scheduled flights in the period
What caused the delays
- Airline (crew, maintenance, cleaning) 91%
- Air traffic control & airport 7%
- Extreme weather 2%
- Late-arriving aircraft 0%
- Security 0%
Share of delay minutes airlines attributed to each cause (BTS).
Houston (IAH) to San Francisco (SFO)
Historically, this flight arrives 15+ minutes late 40% of the time, and when it is late the delay averages 66 minutes. It was cancelled 0.0% of the time.
- On-time arrivals
- 60.0%
- Less than 15 minutes late
- Cancelled
- 0.0%
- Of scheduled flights
- Average delay when late
- 66 min
- Flights arriving 15+ minutes late
- Flights tracked
- 25
- Scheduled flights in the period
What caused the delays
- Late-arriving aircraft 31%
- Airline (crew, maintenance, cleaning) 28%
- Air traffic control & airport 23%
- Extreme weather 18%
- Security 0%
Share of delay minutes airlines attributed to each cause (BTS).
Dayton (DAY) to Denver (DEN)
Historically, this flight arrives 15+ minutes late 8% of the time, and when it is late the delay averages 118 minutes. It was cancelled 0.0% of the time.
- On-time arrivals
- 91.7%
- Less than 15 minutes late
- Cancelled
- 0.0%
- Of scheduled flights
- Average delay when late
- 118 min
- Flights arriving 15+ minutes late
- Flights tracked
- 24
- Scheduled flights in the period
What caused the delays
- Airline (crew, maintenance, cleaning) 88%
- Air traffic control & airport 12%
- Late-arriving aircraft 0%
- Extreme weather 0%
- Security 0%
Share of delay minutes airlines attributed to each cause (BTS).
PBI â ORD
Historically, this flight arrives 15+ minutes late 25% of the time, and when it is late the delay averages 105 minutes. It was cancelled 0.0% of the time.
- On-time arrivals
- 75.0%
- Less than 15 minutes late
- Cancelled
- 0.0%
- Of scheduled flights
- Average delay when late
- 105 min
- Flights arriving 15+ minutes late
- Flights tracked
- 20
- Scheduled flights in the period
What caused the delays
- Air traffic control & airport 49%
- Late-arriving aircraft 40%
- Airline (crew, maintenance, cleaning) 11%
- Extreme weather 0%
- Security 0%
Share of delay minutes airlines attributed to each cause (BTS).
Chicago (ORD) to Minneapolis (MSP)
Only 3 flights 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
- 3
- Scheduled flights in the period
In the news
More headlines →-
United Airlines First Class Steak And Eggs: Great Steak, But Where Were The Eggs?
Live and Let's Fly United Airlines
-
United Airlines Cuts Starlink Installation Timeline to 18 Months as Rollout Accelerates
Drive Tesla Canada United Airlines
-
President Of United Airlines Holdings Makes $4.00M Sale
Benzinga United Airlines
-
From the US to the Costa Smeralda, the number of flights will double in 2027 with United Airlines
Il Sole 24 ORE United Airlines
-
'Actually Did His Job'- Jessica Pegula Takes Aim at United Airlinesâ AI Support With Special Tennis Request for Helpful Employee
Yardbarker United Airlines
-
âOh My God, What?'â â Serena Williamsâ Coach Canât Believe What Jessica Pegula Went Through With United Airlines
Yahoo Sports United Airlines
Headlines found by Google News; stories open on the publisher's site.
Show as table
| Month | On time | Flights |
|---|---|---|
| September 2025 | 86.7% | 30 |
| October 2025 | 80.6% | 31 |
| November 2025 | 63.0% | 27 |
| December 2025 | 87.1% | 31 |
| January 2026 | 87.1% | 31 |
| February 2026 | 82.1% | 28 |
| March 2026 | 90.3% | 31 |
| April 2026 | 96.6% | 29 |
| May 2026 | 83.9% | 31 |
| June 2026 | 80.0% | 30 |
| July 2026 | 87.1% | 31 |
| August 2026 | 76.7% | 31 |
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