Flight number record
OO 4635
SkyWest Airlines · Grand Junction to Denver
- Route
- GJT → DEN
- Departs
- 15:15
- Flights
- 361
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s OO 4635, 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 4635 draws a C. About one flight in three arrives at least 15 minutes late, and the typical late arrival is an hour and a half behind schedule. Build slack into anything you connect to. That rests on 361 flights, with a median arrival 2 minutes early.
The national on-time rate over the same period is 77.3%, so OO 4635 runs 10 points behind the country as a whole. Across a thousand flights that is about 97 extra late arrivals.
Key figures
On time
67.6%
Arrivals under 15 minutes late, of 349 completed flights
Avg delay
86 min
Across delayed arrivals only, not all flights
Cancelled
2.49%
National rate is 1.89%
1 hour+ late
13.8%
National rate is 8.3%
These figures cover 361 flights between September 2025 and August 2026. Beyond the headline rate, 13.8% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Schedule
When OO 4635 flies
OO 4635 flies GJT to DEN without a single fixed slot. Its most common scheduled departure was 15:15, used on 97 of 361 flights, with 15:21 (73 flights) and 15:22 (45 flights) next.
- Departs 15:1597 flights26.9%
- Departs 15:2173 flights20.2%
- Departs 15:2245 flights12.5%
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 15:15 departure sits in the 2pm–5pm window. Across every US flight scheduled in that window the on-time rate is 71.9%, and OO 4635 runs 4 points worse at 67.6%. Midday slots inherit some of the morning's delays without yet carrying the full weight of the evening's.
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Against the route
OO 4635 next to GJT to DEN
Every carrier on GJT to DEN combined arrived on time 79.6% of the time across 2,282 flights, so OO 4635 is 12 points behind it. SkyWest flew 1,550 flights on the same city pair under all its flight numbers, including this one, and those ran 77.0% on time. Across its whole network SkyWest Airlines managed 78.7%, which this flight trails by 11 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| OO 4635thin sample | 361 | 67.6% | 86 min | 2.49% | C |
| All SkyWest Airlines on GJT–DEN | 1,550 | 77.0% | 80 min | 1.81% | B |
| All carriers on GJT–DEN | 2,282 | 79.6% | 75 min | 1.36% | B |
| SkyWest Airlines, whole network | 855,406 | 78.7% | 88 min | 1.79% | B |
Across the year
OO 4635 quarter by quarter
OO 4635 did not run the same all year. Its best quarter was Jan–Mar 2026 at 79.5% on time and its weakest Jul–Sep 2026 at 51.7%, a swing of 28 points on roughly 90 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.
- Jul–Sep 202528 flights—
- Oct–Dec 202591 flights74.1%
- Jan–Mar 202690 flights79.5%
- Apr–Jun 202691 flights68.9%
- Jul–Sep 202661 flights51.7%
Scale runs 45% to 85%. Rows with fewer than 30 flights show a dash.
By weekday, OO 4635 did best on Sunday at 80.0% on time and worst on Thursday at 60.0%. Each day rests on about 52 flights, so a gap of 20 points is worth noticing but could still narrow in another year.
Arrival by arrival
How late OO 4635 runs when it is late
OO 4635 often beats the schedule: 94 of 349 completed flights, 27%, arrived 15 minutes or more early. The 113 late arrivals split 44 under half an hour, 21 between 30 and 60 minutes, and 48 an hour or more.
- 15+ min early94 flights26.9%
- Within 15 min142 flights40.7%
- 15–29 min late44 flights12.6%
- 30–59 min late21 flights6.0%
- 1–2 hours late25 flights7.2%
- 2+ hours late23 flights6.6%
Scale runs 0% to 100%.
Share of 349 completed flights by arrival against schedule.
Time lost at the gate mostly stays lost. Of 87 departures that left 15 minutes late or more, only 10 made it up before arrival. In the other direction, 36 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 4635
The latest arrival of the period was on 11 September 2025, 19 hours 59 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). The five worst days are spread across September, March, June, August and July, with no single month standing out.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 11 September 2025 | 19 hours 59 minutes | Carrier |
| 4 March 2026 | 8 hours | Carrier |
| 6 June 2026 | 6 hours 48 minutes | Late-arriving aircraft |
| 14 August 2026 | 5 hours 28 minutes | National Airspace System |
| 22 July 2026 | 4 hours 50 minutes | National Airspace System |
Delay causes
Why OO 4635 runs late
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 9,679 reported delay minutes.
- 35%National Airspace System
- 34%Carrier
- 21%Late-arriving aircraft
- 10%Extreme weather
35% 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 3,419 minutes out of 9,679, against a national NAS share of 21%. The split is drawn from 9,679 delay minutes reported on OO 4635.
Cancellations sit at 2.49% against a national 1.89%, which is ordinary. Diversions add another 0.83%.
Connections and routes
What a delay on this flight costs
13.8% of arrivals land a full hour or more behind schedule, against 8.3% nationally. Ninety minutes is the honest minimum for a connection here, and two hours if the onward flight is on a separate ticket.
The same number turns up on two other city pairs in the data, including DEN to PSP (1) and DEN to GSO (1), but none flew often enough under OO 4635 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to GJT to DEN only.
One caution: this is a thin sample. 361 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 4635
For a booking, OO 4635 is a flight to put a long connection behind. 13.8% of its completed flights arrived an hour or more late, which a short layover will not absorb. If the onward flight is on a separate ticket, the risk sits with you.
Related
Where to go next
- GJT to DEN, every carrier and departure
- DEN to GJT, the return direction
- SkyWest Airlines 4709 on the same route84.3%
- SkyWest Airlines 5755 on the same route64.3%
- United Airlines 1877 on the same route86.3%
- SkyWest Airlines 4800 on the same route87.4%
- 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
- How often a connection fails at the major US hubs
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.