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Flight Reliability

F9 4721 · Frontier Airlines

Denver → Salt Lake City (DEN–SLC)

87
Pretty Reliable
WanderNerd Reliability Score
81%
Arrive within 15 minutes
3 min
Average arrival delay
0.4%
Cancelled
6 min early
Median arrival delay

Based on 227 historical flights. Data through May 2026.

What the data says

The 3–6 PM departure wins.

F9 4721 departing between 3–6 PM arrived on time 92% of the time, versus 75% between 6–9 AM.

Thursdays have been rough.

F9 4721 arrived on time 94% of the time on Saturdays and just 65% on Thursdays. That gap is worth planning around.

A bit ahead of the DEN–SLC route.

F9 4721 arrived on time 81% of the time, versus 78% across the DEN–SLC route.

Better than the Frontier Airlines network average.

F9 4721 arrived on time 81% of the time, versus 73% across the Frontier Airlines network.

The breakdown

On-time by weekday
  • Mon74%(31 flights)
  • Tue91%(32 flights)
  • Wed77%(31 flights)
  • Thu65%(34 flights)
  • Fri84%(31 flights)
  • Sat94%(32 flights)
  • Sun83%(35 flights)
On-time by departure window
  • 6–9 AM75%(12 flights)
  • 9 AM–12 PM80%(183 flights)
  • 12–3 PM84%(19 flights)
  • 3–6 PM92%(12 flights)
On-time trend by month
87%
Feb

Jun 80% → Feb 87% on time

On-time arrival percentage by month
MonthOn-time percentageFlights
June 202580%30
July 202573%30
August 202593%30
September 202570%30
October 202582%28
November 202587%23
December 202575%16
January 202682%22
February 202687%15
Departures on time
83%
Diverted
0%
Flights flown
226
Months covered
10

Same route, other flights

Keep nerding

Based on 227 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.