Flight number record
OO 4321
SkyWest Airlines · Salt Lake City to St. George
- Route
- SLC → SGU
- Departs
- 13:30
- Flights
- 355
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s OO 4321, 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 4321 earns an A+. Close to nine flights in ten arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 15 points better than the national rate of 77.3%. When something does go wrong the average delay runs a little over an hour. That rests on 355 flights, with a median arrival 12 minutes early.
Set against the rest of the country, OO 4321's record is 15 points better than the US average of 77.3%. That gap is worth roughly 148 fewer late arrivals for every thousand flights.
Key figures
On time
92.1%
Arrivals under 15 minutes late, of 354 completed flights
Avg delay
77 min
Across delayed arrivals only, not all flights
Cancelled
0.00%
National rate is 1.89%
1 hour+ late
2.3%
National rate is 8.3%
These figures cover 355 flights between September 2025 and August 2026. The median arrival is 12 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 4321 flies
OO 4321 is scheduled to leave Salt Lake City (SLC) at 13:30 local time and reach St. George (SGU) at 14:43. That slot held for 294 of the 355 scheduled departures in the data, so the figures below describe one steady operation rather than a number that moved around the clock.
- Departs 13:30294 flights82.8%
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 13:30 departure sits in the 11am–2pm window. Across every US flight scheduled in that window the on-time rate is 78.3%, and OO 4321 runs 14 points better at 92.1%. 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 4321 next to SLC to SGU
Every carrier on SLC to SGU combined arrived on time 91.4% of the time across 1,727 flights, so OO 4321 is about level with it. Across its whole network SkyWest Airlines managed 78.7%, which this flight beats by 13 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| OO 4321thin sample | 355 | 92.1% | 77 min | 0.00% | A+ |
| All SkyWest Airlines on SLC–SGU | 1,727 | 91.4% | 81 min | 0.17% | A+ |
| All carriers on SLC–SGU | 1,727 | 91.4% | 81 min | 0.17% | A+ |
| SkyWest Airlines, whole network | 855,406 | 78.7% | 88 min | 1.79% | B |
Across the year
OO 4321 quarter by quarter
Quarter by quarter OO 4321 held fairly steady: 93.4% in Oct–Dec 2025, 92.2% in Jan–Mar 2026, 92.2% in Apr–Jun 2026 and 85.7% in Jul–Sep 2026. A spread of 8 points is about what a sample of this size moves on its own, so the annual figure is a fair summary.
- Jul–Sep 202528 flights—
- Oct–Dec 202591 flights93.4%
- Jan–Mar 202690 flights92.2%
- Apr–Jun 202690 flights92.2%
- Jul–Sep 202656 flights85.7%
Scale runs 75% to 100%. Rows with fewer than 30 flights show a dash.
By weekday, OO 4321 ranged from 89.6% on Saturday to 94.3% on Monday. With about 51 flights behind each day, a spread of 5 points is inside normal variation, so the day you fly is not worth changing for this flight.
Arrival by arrival
How late OO 4321 runs when it is late
OO 4321 often beats the schedule: 146 of 354 completed flights, 41%, arrived 15 minutes or more early. The 28 late arrivals split 9 under half an hour, 11 between 30 and 60 minutes, and 8 an hour or more.
- 15+ min early146 flights41.2%
- Within 15 min180 flights50.8%
- 15–29 min late9 flights2.5%
- 30–59 min late11 flights3.1%
- 1–2 hours late4 flights1.1%
- 2+ hours late4 flights1.1%
Scale runs 0% to 100%.
Share of 354 completed flights by arrival against schedule.
Time lost at the gate mostly stays lost. Of 23 departures that left 15 minutes late or more, only 0 made it up before arrival. Only 5 left on time and still arrived late.
The worst days
Worst days for OO 4321
The latest arrival of the period was on 11 May 2026, 5 hours 56 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 |
|---|---|---|
| 11 May 2026 | 5 hours 56 minutes | Carrier |
| 13 June 2026 | 4 hours 11 minutes | Carrier |
| 4 December 2025 | 3 hours 25 minutes | Carrier |
| 7 June 2026 | 3 hours 4 minutes | National Airspace System |
| 4 October 2025 | 1 hour 55 minutes | Extreme weather |
Delay causes
Why OO 4321 runs late
Carrier accounts for 75% of the 2,155 delay minutes carriers reported here, and the remaining four split what is left.
- 75%Carrier
- 16%National Airspace System
- 9%Extreme weather
The largest share of delay minutes, 75%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 1,619 of the 2,155 delay minutes reported here. The split is drawn from 2,155 delay minutes reported on OO 4321.
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
Badly late arrivals are rare here: only 2.3% land an hour or more behind schedule, against 8.3% nationally. Connections built on this flight are about as safe as US domestic connections get, though a cancelled flight still ignores every layover you give it.
OO 4321 is not only a SLC to SGU flight. It also flew SGU to SLC (353 flights, 87.3% on time) often enough to be scored on its own. Airlines attach one number to several legs of an aircraft's day, and each leg keeps its own record here, so check which city pair is on your booking before reading a rate.
One caution: this is a thin sample. 355 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.
| Also flown as | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| SGU to SLCthin sample | 353 | 87.3% | 64 min | 0.00% | A+ |
What to do with this
Booking OO 4321
For a booking, OO 4321 has one of the better records a US domestic flight can show: 92.1% on time and 0.00% cancelled. That is a base rate, not a promise about any single day.
Related
Where to go next
- SLC to SGU, every carrier and departure
- SGU to SLC, the return direction
- SkyWest Airlines 4279 on the same route92.2%
- SkyWest Airlines 4253 on the same route93.6%
- SkyWest Airlines 4308 on the same route94.2%
- SkyWest Airlines 4263 on the same route84.0%
- Salt Lake City International (SLC) 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.