Carrier route record

F9DEN→SLC

Frontier Airlines · Denver to Salt Lake City

Flights: 1,010
Period: July 2025 to June 2026
Share of route: 13%
Carriers: 5

Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Frontier Airlines.

Frontier on DEN to SLC lands a B+, 4 points better than the national rate of 77.6%. Roughly one flight in five arrives 15 minutes late or worse, and those flights are late by about an hour on average. That is a workable record, not a spotless one. That rests on 1,010 flights. The strongest carrier on the route with a full sample, Delta Air Lines, flew 1,689 at 82.3% on time.

Delta Air Lines is the most reliable of the four carriers covered here at 82.3% on time across 1,689 flights.

On time

81.7%

Arrivals under 15 minutes late, of 1,005 completed flights

Avg delay

60 min

Across delayed arrivals only, not all flights

Cancelled

0.50%

National rate is 1.81%

Whole route

77.5%

Every carrier on DEN to SLC, 7,758 flights

These figures cover 1,010 flights between July 2025 and June 2026. The median arrival is 10 minutes early, which is the part an average hides: most flights here are fine, and the on-time rate is decided by a tail of badly late ones. On-time means under 15 minutes late, the DOT's own threshold.

Carrier by carrier

Frontier against every carrier on DEN to SLC

Frontier flew 1,010 of the 7,758 flights on DEN to SLC, about 13% of it. Its 81.7% on time is 4 points better than the route as a whole, which runs 77.5%. Ranked by on-time rate it is number two of five carriers on the route, where the range runs from Delta at 82.3% to Southwest at 71.2%.

The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 82.3% of the time; Southwest Airlines manages 71.2%. Sample sizes sit next to every figure, because a two-point gap across 2,329 flights means less than a ten-point one.

On-time performance by carrier on DEN to SLC
Airline	Flights	On time	Avg delay	Cancelled	Grade
Delta Air Lines	1,689	82.3%	81 min	0.41%	B+
Frontier Airlines (this page)	1,010	81.7%	60 min	0.50%	B+
SkyWest Airlines	1,399	79.4%	64 min	0.86%	B+
United Airlines	1,331	77.5%	58 min	0.15%	B+
Southwest Airlines	2,329	71.2%	52 min	0.47%	C+

Delta leads Southwest by 11 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.

Flight by flight

Frontier flight numbers on DEN to SLC

F9 425122:2969.2% · 255 flights

Departure window

When Frontier runs best on this route

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 23 points, against 11 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am248 flights95.2%
8am–11am190 flights79.9%
11am–2pm127 flights84.1%
2pm–5pm78 flights82.1%
5pm–8pm30 flights73.3%
8pm–5am337 flights72.5%

Scale runs 65% to 100%. Rows with fewer than 30 flights show a dash.

Book the early departure. Flights leaving between 5am–8am arrive on time 95.2% of the time, against 72.5% for the overnight window. That is 23 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 8pm–5am window is the busiest, with 337 flights scheduled in it.

Across the year

Frontier on DEN to SLC through the year

Darker means more delays. Figures are on-time percentages.April best, July worst

July is the worst month at 69.6% on time, 23 points below April, the best at 92.7%. Summer afternoon convection and peak-season schedules land on the same weeks every year, so this is a pattern you can book around rather than a run of bad luck. June was the busiest month here, with 95 flights.

Across the week, Tuesday is the strongest day at 87.8% on time and Sunday the weakest at 77.0%. 11 points is a smaller lever than departure hour, but it is free.

Delay causes

Why Frontier runs late on this route

Carriers report a reason for every delay minute they cause, in five DOT categories. The split below is by minutes, not by number of flights, so a handful of very long weather delays weighs as much as many short ones. It covers 11,000 reported delay minutes.

Late-arriving aircraft
41%
Carrier
34%
National Airspace System
17%
Extreme weather
8%

41% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. That is a cascade, and cascades start small and grow through the day. Across 11,000 reported delay minutes here, that single category outweighs weather by 5 to one. It is the strongest argument for booking the first departure of the morning, when the aircraft has been sitting at the gate overnight with nothing to inherit. The split is drawn from 11,113 reported delay minutes.

The practical consequence: the 5am–8am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 95.2% on time here.

Cancellations are rare at 0.50%, below the national 1.81% and low enough to earn the plus on the grade. Roughly one flight in 100 is called off; the risk here is arriving late, not not arriving.

Connections and stage length

What a delay here costs

5.9% of arrivals land an hour or more late, close to the national 8.1%. That is the figure that decides a connection, and it says a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last about an hour, which a normal layover absorbs.

At 391 miles this is a short hop, and stage length matters more than it looks. A flight this short spends under two hours in the air, which leaves almost nothing to claw back a late pushback with. Delay here is decided on the ground, in the turn, which is why the 5am–8am window matters as much as it does.

The return leg is a different operation and performs like one: it runs 78.1% on time across 1,012 flights, 4 points below this direction. Departure banks, aircraft rotations and the congestion at each end all differ, so scoring the two directions together would average away a real 4 points of difference.

One caution: this is a thin sample. 1,010 flights over twelve months is enough to clear this site's floor but not enough to pin the rate down tightly, and a single bad week moves it by more than a point. Treat the grade as a rough reading.

What to do with this

Booking Frontier on DEN to SLC

Put together: treat all of this as provisional. 1,010 flights over twelve months is enough to clear this site's floor and not enough to be confident to better than a couple of points. The 81.7% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 1,005 completed flights over 12 months sit behind that.

Where to go next

Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.

Key figures