Carrier route record

F9PDX→DEN

Frontier Airlines · Portland to Denver

Flights: 312
Period: July 2025 to June 2026
Share of route: 7%
Carriers: 5

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

Frontier on PDX to DEN lands a B+, level with the national rate of 77.6%. Roughly one flight in four 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 312 flights. The strongest carrier on the route with a full sample, United Airlines, flew 1,820 at 90.2% on time.

United Airlines is the most reliable of the three carriers covered here at 90.2% on time across 1,820 flights.

On time

77.3%

Arrivals under 15 minutes late, of 308 completed flights

Avg delay

61 min

Across delayed arrivals only, not all flights

Cancelled

0.96%

National rate is 1.81%

Whole route

80.8%

Every carrier on PDX to DEN, 4,290 flights

These figures cover 312 flights between July 2025 and June 2026. Beyond the headline rate, 9.1% of arrivals land a full hour or more behind schedule. That is the number that wrecks a connection, and it is not visible in an on-time percentage alone.

Carrier by carrier

Frontier against every carrier on PDX to DEN

Frontier flew 312 of the 4,290 flights on PDX to DEN, about 7% of it. Its 77.3% on time is 4 points worse than the route as a whole, which runs 80.8%. Ranked by on-time rate it is number two of five carriers on the route, where the range runs from United at 90.2% to SkyWest at 69.2%. One of those carriers flew fewer than 365 flights here, so treat their positions as rough.

The choice of carrier is not cosmetic here. United Airlines arrives on time 90.2% of the time; Southwest Airlines manages 72.2%. Sample sizes sit next to every figure, because a two-point gap across 1,563 flights means less than a ten-point one.

On-time performance by carrier on PDX to DEN
Airline	Flights	On time	Avg delay	Cancelled	Grade
United Airlines	1,820	90.2%	71 min	0.55%	A+
Frontier Airlines (this page)thin sample	312	77.3%	61 min	0.96%	B+
Alaska Airlines	582	76.8%	52 min	0.34%	B+
Southwest Airlines	1,563	72.2%	49 min	0.26%	C+
SkyWest Airlinesthin sample	13	69.2%	39 min	0.00%	C+

The spread between United and Southwest is 18 points, wide enough that it should decide the booking. On a hundred trips that is 18 more arrivals inside the on-time window.

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 22 points, against 18 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am94 flights71.7%
8am–11am4 flights—
11am–2pm141 flights84.3%
2pm–5pm22 flights—
5pm–8pm51 flights62.0%
8pm–5am—

Scale runs 55% to 90%. Rows with fewer than 30 flights show a dash.

The 5pm–8pm window is where this operation falls apart: 62.0% on time, against 84.3% for the 11am–2pm slot. By evening the aircraft flying these rotations have absorbed a full day of small delays and there is no slack left to recover in. The 11am–2pm window is the busiest, with 141 flights scheduled in it.

Across the year

Frontier on PDX to DEN through the year

Jul–Sep 2025149 flights67.8%
Oct–Dec 202568 flights85.3%
Jan–Mar 202623 flights—
Apr–Jun 202672 flights91.5%

Scale runs 60% to 95%. Rows with fewer than 30 flights show a dash.

Monthly volumes are too low here to break the year into twelve reliable readings. What the twelve-month total says is 77.3% on time across 312 flights.

Frontier on PDX to DEN did not run the same all year. Its best quarter was Apr–Jun 2026 at 91.5% on time and its weakest Jul–Sep 2025 at 67.8%, a swing of 24 points on roughly 104 flights a quarter. The twelve-month rate averages over that, so if you are flying in a weak quarter the quarter's own figure is the better guide.

Across the week, Tuesday is the strongest day at 82.5% on time and Wednesday the weakest at 61.3%. 21 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 4,268 reported delay minutes.

Late-arriving aircraft
35%
National Airspace System
34%
Carrier
31%
Extreme weather
1%

35% 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 4,268 reported delay minutes here, that single category outweighs weather by 35 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 4,268 reported delay minutes.

34% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 1,443 minutes out of 4,268, against a national NAS share of 21%.

Cancellations sit at 0.96% against a national 1.81%, which is ordinary. Diversions add another 0.32%.

Connections and stage length

What a delay here costs

For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 9.1% of arrivals land a full hour or more behind schedule, against 8.1% nationally. A 45-minute layover does not survive that, and no amount of walking quickly changes it. Ninety minutes is the honest minimum here, and two hours if the onward flight is on a separate ticket.

The 991 miles between these two airports put this in the middle of the US network, around two and a half to three hours of block time. That is enough cruise to absorb a ten-minute late pushback and not enough to absorb thirty. It is also long enough that the aircraft usually flies three or four legs a day rather than six, which slows how fast delay compounds.

The return leg is a different operation and performs like one: it runs 80.3% on time across 311 flights, 3 points above 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 3 points of difference.

One caution: this is a thin sample. 312 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 PDX to DEN

Put together: treat all of this as provisional. 312 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 77.3% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 308 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