Flight Reliability
F9 4251 · Frontier Airlines
Denver → Salt Lake City (DEN–SLC)
73
Usually Fine
WanderNerd Reliability Score
- 69%
- Arrive within 15 minutes
- 13 min
- Average arrival delay
- 0.8%
- Cancelled
- 4 min early
- Median arrival delay
Based on 248 historical flights. Data through May 2026.
What the data says
Sunday scaries are real for this one.
F9 4251 arrived on time 84% of the time on Saturdays and just 59% on Sundays. That gap is worth planning around.
Lagging the DEN–SLC route.
F9 4251 arrived on time 69% of the time, versus 78% across the DEN–SLC route.
A bit behind the Frontier Airlines network.
F9 4251 arrived on time 69% of the time, versus 73% across the Frontier Airlines network.
Trending in the right direction.
F9 4251 arrived on time 86% of the time over the last three months in the data, compared with 68% in the three months before that.
The breakdown
- Mon71%(49 flights)
- Tue—(9 flights)
- Wed75%(20 flights)
- Thu71%(49 flights)
- Fri61%(49 flights)
- Sat84%(19 flights)
- Sun59%(51 flights)
92%
May
Jun 52% → May 92% on time
| Month | On-time percentage | Flights |
|---|---|---|
| June 2025 | 52% | 23 |
| July 2025 | 50% | 20 |
| August 2025 | 55% | 20 |
| September 2025 | 65% | 17 |
| October 2025 | 72% | 18 |
| November 2025 | 76% | 21 |
| December 2025 | 68% | 25 |
| January 2026 | 63% | 19 |
| February 2026 | 74% | 19 |
| March 2026 | 79% | 29 |
| April 2026 | 86% | 22 |
| May 2026 | 92% | 13 |
- Departures on time
- 63%
- Diverted
- 0%
- Flights flown
- 246
- Months covered
- 12
Same route, other flights
Keep nerding
Based on 248 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.