Flight number record

OO 4635

SkyWest Airlines · Grand Junction to Denver

Route: GJT → DEN
Departs: 15:21
Flights: 362
Period: July 2025 to June 2026

Historical statistics for July 2025 to June 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 a little over an hour behind schedule. Build slack into anything you connect to. That rests on 362 flights, with a median arrival 1 minute late.

The national on-time rate over the same period is 77.6%, so OO 4635 runs 12 points behind the country as a whole. Across a thousand flights that is about 123 extra late arrivals.

On time

65.3%

Arrivals under 15 minutes late, of 349 completed flights

Avg delay

81 min

Across delayed arrivals only, not all flights

Cancelled

2.76%

National rate is 1.81%

1 hour+ late

13.8%

National rate is 8.1%

These figures cover 362 flights between July 2025 and June 2026. Beyond the headline rate, 13.8% 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.

Schedule

When OO 4635 flies

OO 4635 flies GJT to DEN without a single fixed slot. Its most common scheduled departure was 15:21, used on 122 of 362 flights, with 15:15 (57 flights) and 15:22 (45 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.

Departs 15:21122 flights33.7%
Departs 15:1557 flights15.7%
Departs 15:2245 flights12.4%

Scale runs 0% to 100%. Rows with fewer than 30 flights show a dash.

Share of scheduled departures at each local time. Times used on fewer than one flight in ten are not listed.

A 15:21 departure sits in the 2pm–5pm window. Across every US flight scheduled in that window the on-time rate is 72.4%, and OO 4635 runs 7 points worse at 65.3%. Midday slots inherit some of the morning's delays without yet carrying the full weight of the evening's.

Against the route

OO 4635 next to GJT to DEN

Every carrier on GJT to DEN combined arrived on time 77.6% of the time across 2,229 flights, so OO 4635 is 12 points behind it. SkyWest flew 1,496 flights on the same city pair under all its flight numbers, including this one, and those ran 75.5% on time. Across its whole network SkyWest Airlines managed 79.0%, which this flight trails by 14 points.

OO 4635 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
OO 4635thin sample	362	65.3%	81 min	2.76%	C
All SkyWest Airlines on GJT–DEN	1,496	75.5%	78 min	2.01%	B
All carriers on GJT–DEN	2,229	77.6%	75 min	1.48%	B
SkyWest Airlines, whole network	852,935	79.0%	88 min	1.77%	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 2025 at 38.4%, a swing of 41 points on roughly 91 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 202590 flights38.4%
Oct–Dec 202591 flights74.1%
Jan–Mar 202690 flights79.5%
Apr–Jun 202691 flights68.9%

Scale runs 30% to 85%. Rows with fewer than 30 flights show a dash.

By weekday, OO 4635 did best on Sunday at 82.0% on time and worst on Monday at 56.9%. Each day rests on about 52 flights, so a gap of 25 points is worth noticing but could still narrow in another year.

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 9,768 reported delay minutes.

National Airspace System
37%
Carrier
31%
Late-arriving aircraft
20%
Extreme weather
12%

Extreme weather accounts for 12% of delay minutes, well above the single-digit share typical across the system. Weather delays are lumpy: they arrive as whole bad days rather than as a steady drag, so the quarterly figures above are the more useful view of the risk. The national share is 6%, so this operation carries roughly 1.9 times the usual weather exposure. The split is drawn from 9,768 delay minutes reported on OO 4635.

Cancellations run at 2.76%, against 1.81% nationally. That is roughly one flight in 40 cancelled outright. A cancelled flight is invisible in every on-time figure on this page, so the punctuality numbers above describe only the flights that actually operated.

Connections and routes

What a delay on this flight costs

For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 13.8% 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 same number turns up on one other city pair in the data, including 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. 362 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, the cancellation rate is the figure to plan around on OO 4635: 2.76% of its 362 scheduled flights did not operate. A late arrival costs a little over an hour, but a cancellation costs the day, so leave a later option open.

Where to go next

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, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.

Key figures