Route reliability record
RDU→DEN
Raleigh to Denver
- Flights
- 1,734
- Period
- September 2025 to August 2026
- Distance
- 1,436 mi
- Carriers
- 3
This route lands a B+, 5 points better than the national rate of 77.3%. About one flight in six arrives 15 minutes late or worse, and those flights are late by a little over an hour on average. That rests on 1,734 RDU to DEN flights, of which United Airlines flew 727 at 87.7% on time.
Best time to fly RDU to DEN: a 11am–2pm departure, ideally on a Tuesday. Flights in that window arrived on time 94.4% of the time and Tuesday flights 86.8%, against 81.9% for the route overall.
Set against the rest of the country, this route's record is 5 points better than the US average of 77.3%. That gap is worth roughly 46 fewer late arrivals for every thousand flights.
Key figures
On time
81.9%
Arrivals under 15 minutes late, of 1,715 completed flights
Avg delay
68 min
Across delayed arrivals only, not all flights
Cancelled
0.75%
National rate is 1.89%
Best carrier
United
87.7% on time across 727 flights
These figures cover 1,734 flights between September 2025 and August 2026. The median arrival is 7 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.
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Carrier by carrier
Which airline is most reliable on RDU to DEN
The choice of carrier is not cosmetic here. United Airlines arrives on time 87.7% of the time; Southwest Airlines manages 74.8%. Sample sizes sit next to every figure, because a two-point gap across 710 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 727 | 87.7% | 89 min | 0.41% | A+ |
| Frontier Airlinesthin sample | 297 | 84.6% | 79 min | 1.01% | B |
| Southwest Airlines | 710 | 74.8% | 55 min | 0.99% | C+ |
The spread between United and Southwest is 13 points, wide enough that it should decide the booking. On a hundred trips that is 13 more arrivals inside the on-time window.
Flight by flight
Flights on RDU to DEN
The flight numbers below flew this route at least 250 times in the period, busiest first. Each has its own record, with its schedule and delay causes.
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Best ways to make this trip
The most reliable ways to fly Raleigh to Denver
Every airline on this route, ranked by how often a scheduled flight actually operated and arrived on time, with its best departure time and most punctual flight number. No nearby airport pair beat these.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. RDU → DENRaleigh to Denver | United Airlines | 87.3% | 87.7% | 0.41% | 8am–11am, Tue | UA 2288 16:22 |
| 2. RDU → DENRaleigh to Denver | Southwest Airlines | 74.1% | 74.8% | 0.99% | 5am–8am, Tue | — |
Success is the share of scheduled flights that operated and arrived less than 15 minutes late, so a cancelled flight counts against it. “(route)” means the best time comes from every carrier on the route rather than this airline alone.
Departure window
The best time of day to leave
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 30 points, against 13 points between the best and worst carrier.
- 5am–8am322 flights92.1%
- 8am–11am412 flights92.7%
- 11am–2pm110 flights94.4%
- 2pm–5pm428 flights78.5%
- 5pm–8pm411 flights64.9%
- 8pm–5am51 flights70.0%
Scale runs 55% to 100%.
The 5pm–8pm window is where this operation falls apart: 64.9% on time, against 94.4% 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 2pm–5pm window is the busiest, with 428 flights scheduled in it.
Explore
Filter RDU to DEN by airline, time, month and day
Pick a breakdown and a carrier. The dashed mark on each row is the same slice for every US flight.
On RDU to DEN, the best departure window is 11am–2pm at 94.4% on time and the worst is 5pm–8pm at 64.9%, a wide gap of 29.5 points. All US flights leaving 11am–2pm ran 78.3%.
- 5–8am92.1%
- 8–11am92.7%
- 11am–2pm94.4%
- 2–5pm78.5%
- 5–8pm64.9%
- 8pm–5am70.0%
best all US flightsScale 55% to 100%.
Across the year
When delays peak on this route
This route's year swings by 19 points from best month to worst, which is wide. An annual average tells you very little about the week you are actually flying, so read the strip rather than the headline if your dates are fixed.
December is the weak month at 69.9% on time, against 89.0% in May. Winter delays cluster: a single storm system can account for most of a month's shortfall, so an average December hides both very good weeks and genuinely unflyable days. July was the busiest month here, with 157 flights.
Across the week, Tuesday is the strongest day at 86.8% on time and Friday the weakest at 77.7%, a spread of 9 points.
Delay causes
Why this route gets delayed
Late-arriving aircraft accounts for 44% of the 21,000 delay minutes carriers reported here, and the remaining four split what is left.
- 44%Late-arriving aircraft
- 26%Carrier
- 24%National Airspace System
- 5%Extreme weather
- 1%Security
44% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 21,000 reported delay minutes here, that single category outweighs weather by 9 to one. The split is drawn from 21,104 reported delay minutes.
Cancellations are rare at 0.75%, below the national 1.89% 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 actually costs
6.1% of arrivals land an hour or more late, close to the national 8.3%, so a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last a little over an hour, which a normal layover absorbs.
The 1,436 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.
The return leg is a different operation and performs like one: it runs 76.0% on time across 1,732 flights, 6 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 6 points of difference.
The sample behind these figures is 1,734 flights, enough that the headline rate is stable to within roughly a point. The hour-block and month splits divide that further, so read the thinner bars with more caution than the headline.
Work out the risk of missing a connection in DEN after this flight
What to do with this
Booking this route
Put together: the calendar is the biggest lever here, not the carrier or the hour. May runs 89.0% on time and December 69.9%, a swing of 19 points. If the dates move at all, move them out of December before you think about anything else. 1,715 completed flights over 12 months sit behind that.
Common questions
RDU to DEN questions
How often is RDU to DEN delayed?
About one flight in six arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 18.1% of the 1,734 flights in this analysis, against 22.7% nationally. Delayed flights are late by a little over an hour on average.
Which airline is most reliable on RDU to DEN?
United Airlines leads at 87.7% on time across 727 flights. Southwest Airlines is at the other end on 74.8%, a gap of 13 points. Sample size matters as much as the percentage: a rate built from a few hundred flights moves around far more than one built from ten thousand.
What time of day has the fewest delays on RDU to DEN?
The 11am–2pm departure window is the strongest at 94.4% on time. The 5pm–8pm window is the weakest at 64.9%, 30 points behind. Later departures inherit delays from earlier flights the same aircraft has already flown, which is why the curve slopes the way it does.
How bad are December delays on RDU to DEN?
December is the weakest month at 69.9% on time, compared with 89.0% in May. Across the year that is 19 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.
Related
Where to go next
- DEN to RDU — the return legseparate record
- Raleigh-Durham International (RDU) delay statistics
- Denver International (DEN) delay statistics
- United Airlines on RDU to DEN87.7%
- Frontier Airlines on RDU to DEN84.6%
- Southwest Airlines on RDU to DEN74.8%
- RDU to ATL, a related route86.5%
- PHX to DEN, a related route76.7%
- RDU to ORD, a related route74.3%
- United Airlines on-time record87.7%
- Frontier Airlines on-time record84.6%
- Southwest Airlines on-time record74.8%
- Same route, different airline: where the carrier you pick matters most
- Why the first flight of the morning is statistically safest
Direction matters. RDU to DEN and DEN to RDU are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
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Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.