Flight number record
OO 4631
SkyWest Airlines · Casper to Denver
- Route
- CPR → DEN
- Departs
- 09:00
- Flights
- 309
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s OO 4631, check with SkyWest Airlines. SkyWest Airlines flies under contract for larger airlines, so a ticket for this flight may show a different airline code and number.
OO 4631 lands a B+, 7 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 an hour and a half on average. That rests on 309 flights, with a median arrival 5 minutes early.
Set against the rest of the country, OO 4631's record is 7 points better than the US average of 77.3%. That gap is worth roughly 65 fewer late arrivals for every thousand flights.
Key figures
On time
83.8%
Arrivals under 15 minutes late, of 308 completed flights
Avg delay
97 min
Across delayed arrivals only, not all flights
Cancelled
0.00%
National rate is 1.89%
1 hour+ late
5.2%
National rate is 8.3%
These figures cover 309 flights between September 2025 and August 2026. The median arrival is 5 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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Schedule
When OO 4631 flies
OO 4631 flies CPR to DEN without a single fixed slot. Its most common scheduled departure was 09:00, used on 101 of 309 flights, with 09:26 (82 flights) and 09:03 (53 flights) next.
- Departs 09:00101 flights32.7%
- Departs 09:2682 flights26.5%
- Departs 09:0353 flights17.2%
Scale runs 0% to 100%.
Share of scheduled departures at each local time. Times used on fewer than one flight in ten are not listed.
A 09:00 departure sits in the 8am–11am window. Across every US flight scheduled in that window the on-time rate is 83.9%, and OO 4631 runs level with that at 83.8%. Early departures usually start with an aircraft that has not flown yet that day, which is most of why the window does well.
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Against the route
OO 4631 next to CPR to DEN
Every carrier on CPR to DEN combined arrived on time 83.1% of the time across 2,629 flights, so OO 4631 is about level with it. Across its whole network SkyWest Airlines managed 78.7%, which this flight beats by 5 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| OO 4631thin sample | 309 | 83.8% | 97 min | 0.00% | B+ |
| All SkyWest Airlines on CPR–DEN | 2,629 | 83.1% | 91 min | 0.95% | B+ |
| All carriers on CPR–DEN | 2,629 | 83.1% | 91 min | 0.95% | B+ |
| SkyWest Airlines, whole network | 855,406 | 78.7% | 88 min | 1.79% | B |
Across the year
OO 4631 quarter by quarter
OO 4631 did not run the same all year. Its best quarter was Jul–Sep 2026 at 93.5% on time and its weakest Jan–Mar 2026 at 77.5%, a swing of 16 points on roughly 77 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.
- Oct–Dec 202567 flights83.6%
- Jan–Mar 202689 flights77.5%
- Apr–Jun 202691 flights83.3%
- Jul–Sep 202662 flights93.5%
Scale runs 70% to 100%.
By weekday, OO 4631 ranged from 79.5% on Friday to 91.1% on Sunday. With about 44 flights behind each day, a spread of 12 points is inside normal variation, so the day you fly is not worth changing for this flight.
Arrival by arrival
How late OO 4631 runs when it is late
OO 4631 often beats the schedule: 91 of 308 completed flights, 30%, arrived 15 minutes or more early. The 50 late arrivals split 18 under half an hour, 16 between 30 and 60 minutes, and 16 an hour or more.
- 15+ min early91 flights29.5%
- Within 15 min167 flights54.2%
- 15–29 min late18 flights5.8%
- 30–59 min late16 flights5.2%
- 1–2 hours late6 flights1.9%
- 2+ hours late10 flights3.2%
Scale runs 0% to 100%.
Share of 308 completed flights by arrival against schedule.
11 of 39 late departures made up the time and arrived on time, 28% of them. In the other direction, 22 flights left on time yet arrived 15 minutes late or more, so that delay built up after pushback: in the air, in a holding pattern or on the ground at DEN.
The worst days
Worst days for OO 4631
The latest arrival of the period was on 17 April 2026, 10 hours 33 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). The same cause led on three of the five worst days.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 17 April 2026 | 10 hours 33 minutes | Carrier |
| 10 March 2026 | 10 hours 30 minutes | National Airspace System |
| 19 December 2025 | 7 hours 16 minutes | Carrier |
| 3 April 2026 | 6 hours 25 minutes | Extreme weather |
| 2 March 2026 | 5 hours 4 minutes | Carrier |
Delay causes
Why OO 4631 runs late
Carrier accounts for 61% of the 4,856 delay minutes carriers reported here, and the remaining four split what is left.
- 61%Carrier
- 20%National Airspace System
- 11%Late-arriving aircraft
- 8%Extreme weather
The largest share of delay minutes, 61%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 2,979 of the 4,856 delay minutes reported here. The split is drawn from 4,856 delay minutes reported on OO 4631.
Cancellations are rare at 0.00%, below the national 1.89% and low enough to earn the plus on the grade. Almost no flights are called off; the risk here is arriving late, not not arriving.
Connections and routes
What a delay on this flight costs
5.2% 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 an hour and a half, which a normal layover absorbs.
The same number turns up on three other city pairs in the data, including DEN to ICT (31), MOT to DEN (24) and FAR to ORD (1), but none flew often enough under OO 4631 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to CPR to DEN only.
One caution: this is a thin sample. 309 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 OO 4631
For a booking, read OO 4631 as 83.8% on time with 0.00% cancelled over 309 flights. Those are rates from the past twelve months, not a forecast for any particular day.
Related
Where to go next
- CPR to DEN, every carrier and departure
- DEN to CPR, the return direction
- SkyWest Airlines 5245 on the same route84.0%
- SkyWest Airlines 5818 on the same route88.1%
- SkyWest Airlines 4658 on the same route88.5%
- SkyWest Airlines 5513 on the same route91.6%
- SkyWest Airlines 4666 on the same route77.1%
- SkyWest Airlines 5809 on the same route77.1%
- Denver International (DEN) delay statistics
- SkyWest Airlines on-time record
- Every SkyWest Airlines flight number with a record
- The most and least reliable flight numbers in the US
- Worst months to fly in the US, ranked by the data
A flight number here means SkyWest Airlines’s own number as it reports to the DOT. How the figures are computed is on the methodology page.
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.