Flight number record
OO 4031
SkyWest Airlines · Seattle to Ontario
- Route
- SEA → ONT
- Departs
- 14:30
- Flights
- 348
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s OO 4031, 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 4031 earns an A+. More than four flights in five arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 9 points better than the national rate of 77.3%. When something does go wrong the average delay runs about 45 minutes. That rests on 348 flights, with a median arrival 7 minutes early.
Set against the rest of the country, OO 4031's record is 9 points better than the US average of 77.3%. That gap is worth roughly 94 fewer late arrivals for every thousand flights.
Key figures
On time
86.7%
Arrivals under 15 minutes late, of 347 completed flights
Avg delay
45 min
Across delayed arrivals only, not all flights
Cancelled
0.29%
National rate is 1.89%
1 hour+ late
2.3%
National rate is 8.3%
These figures cover 348 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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Schedule
When OO 4031 flies
OO 4031 flies SEA to ONT without a single fixed slot. Its most common scheduled departure was 14:30, used on 143 of 348 flights, with 11:15 (64 flights) and 14:19 (39 flights) next.
- Departs 14:30143 flights41.1%
- Departs 11:1564 flights18.4%
- Departs 14:1939 flights11.2%
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 14:30 departure sits in the 2pm–5pm window. Across every US flight scheduled in that window the on-time rate is 71.9%, and OO 4031 runs 15 points better at 86.7%. 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 4031 next to SEA to ONT
Every carrier on SEA to ONT combined arrived on time 82.6% of the time across 2,487 flights, so OO 4031 is 4 points ahead of it. SkyWest flew 1,053 flights on the same city pair under all its flight numbers, including this one, and those ran 88.3% on time. Across its whole network SkyWest Airlines managed 78.7%, which this flight beats by 8 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| OO 4031thin sample | 348 | 86.7% | 45 min | 0.29% | A+ |
| All SkyWest Airlines on SEA–ONT | 1,053 | 88.3% | 52 min | 0.38% | A+ |
| All carriers on SEA–ONT | 2,487 | 82.6% | 50 min | 1.05% | B |
| SkyWest Airlines, whole network | 855,406 | 78.7% | 88 min | 1.79% | B |
Across the year
OO 4031 quarter by quarter
OO 4031 did not run the same all year. Its best quarter was Jul–Sep 2025 at 96.7% on time and its weakest Jul–Sep 2026 at 68.9%, a swing of 28 points on roughly 70 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 202530 flights96.7%
- Oct–Dec 202580 flights92.5%
- Jan–Mar 202686 flights88.2%
- Apr–Jun 202691 flights89.0%
- Jul–Sep 202661 flights68.9%
Scale runs 60% to 100%.
By weekday, OO 4031 ranged from 82.0% on Thursday to 91.8% on Friday. With about 50 flights behind each day, a spread of 10 points is inside normal variation, so the day you fly is not worth changing for this flight.
Arrival by arrival
How late OO 4031 runs when it is late
OO 4031 often beats the schedule: 92 of 347 completed flights, 27%, arrived 15 minutes or more early. Most of the lateness is short. 25 of the 46 late arrivals were under half an hour behind, and 8 reached an hour or more.
- 15+ min early92 flights26.5%
- Within 15 min209 flights60.2%
- 15–29 min late25 flights7.2%
- 30–59 min late13 flights3.7%
- 1–2 hours late5 flights1.4%
- 2+ hours late3 flights0.9%
Scale runs 0% to 100%.
Share of 347 completed flights by arrival against schedule.
5 of 36 late departures made up the time and arrived on time, 14% of them. 15 flights left on time and still arrived late.
The worst days
Worst days for OO 4031
The latest arrival of the period was on 14 August 2026, 3 hours 52 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). The same cause led on four of the five worst days.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 14 August 2026 | 3 hours 52 minutes | Carrier |
| 16 July 2026 | 2 hours 54 minutes | National Airspace System |
| 13 April 2026 | 2 hours 35 minutes | Carrier |
| 25 August 2026 | 1 hour 56 minutes | Carrier |
| 9 July 2026 | 1 hour 53 minutes | Carrier |
Delay causes
Why OO 4031 runs late
Carrier accounts for 74% of the 2,058 delay minutes carriers reported here, and the remaining four split what is left.
- 74%Carrier
- 20%National Airspace System
- 6%Extreme weather
The largest share of delay minutes, 74%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 1,532 of the 2,058 delay minutes reported here. The split is drawn from 2,058 delay minutes reported on OO 4031.
Cancellations are rare at 0.29%, 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 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.
The 956 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.
OO 4031 is not only a SEA to ONT flight. It also flew ONT to SEA (322 flights, 88.5% 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. 348 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 |
|---|---|---|---|---|---|
| ONT to SEAthin sample | 322 | 88.5% | 72 min | 0.31% | A+ |
What to do with this
Booking OO 4031
For a booking, OO 4031 has one of the better records a US domestic flight can show: 86.7% on time and 0.29% cancelled. That is a base rate, not a promise about any single day.
Related
Where to go next
- SEA to ONT, every carrier and departure
- ONT to SEA, the return direction
- Alaska Airlines 1364 on the same route90.1%
- Seattle-Tacoma International (SEA) delay statistics
- Ontario International (ONT) 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.