Flight number record

OO 4031

SkyWest Airlines · Seattle to Ontario

Route: SEA → ONT
Departs: 14:30
Flights: 347
Period: July 2025 to June 2026

Historical statistics for July 2025 to June 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+. Close to nine flights in ten arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 12 points better than the national rate of 77.6%. When something does go wrong the average delay runs roughly 35 minutes. That rests on 347 flights, with a median arrival 9 minutes early.

Set against the rest of the country, OO 4031's record is 12 points better than the US average of 77.6%. That gap is worth roughly 120 fewer late arrivals for every thousand flights.

On time

89.6%

Arrivals under 15 minutes late, of 346 completed flights

Avg delay

37 min

Across delayed arrivals only, not all flights

Cancelled

0.29%

National rate is 1.81%

1 hour+ late

1.2%

National rate is 8.1%

These figures cover 347 flights between July 2025 and June 2026. The median arrival is 9 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.

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 91 of 347 flights, with 11:15 (64 flights) and 14:20 (39 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.

Departs 14:3091 flights26.2%
Departs 11:1564 flights18.4%
Departs 14:2039 flights11.2%

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 14:30 departure sits in the 2pm–5pm window. Across every US flight scheduled in that window the on-time rate is 72.4%, and OO 4031 runs 17 points better at 89.6%. Midday slots inherit some of the morning's delays without yet carrying the full weight of the evening's.

Against the route

OO 4031 next to SEA to ONT

Every carrier on SEA to ONT combined arrived on time 82.9% of the time across 2,550 flights, so OO 4031 is 7 points ahead of it. SkyWest flew 1,084 flights on the same city pair under all its flight numbers, including this one, and those ran 89.7% on time. Across its whole network SkyWest Airlines managed 79.0%, which this flight beats by 11 points.

OO 4031 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
OO 4031thin sample	347	89.6%	37 min	0.29%	A+
All SkyWest Airlines on SEA–ONT	1,084	89.7%	52 min	0.37%	A+
All carriers on SEA–ONT	2,550	82.9%	50 min	1.25%	B
SkyWest Airlines, whole network	852,935	79.0%	88 min	1.77%	B

Across the year

OO 4031 quarter by quarter

Quarter by quarter OO 4031 held fairly steady: 88.9% in Jul–Sep 2025, 92.5% in Oct–Dec 2025, 88.2% in Jan–Mar 2026 and 89.0% in Apr–Jun 2026. A spread of 4 points is about what a sample of this size moves on its own, so the annual figure is a fair summary.

Jul–Sep 202590 flights88.9%
Oct–Dec 202580 flights92.5%
Jan–Mar 202686 flights88.2%
Apr–Jun 202691 flights89.0%

Scale runs 80% to 100%. Rows with fewer than 30 flights show a dash.

By weekday, OO 4031 ranged from 88.0% on Monday to 91.8% on Sunday. With about 50 flights behind each day, a spread of 4 points is inside normal variation, so the day you fly is not worth changing for this flight.

Delay causes

Why OO 4031 runs late

One category carries most of the weight here. Carrier accounts for 79% of the 1,333 delay minutes carriers reported, and the remaining four split what is left. The split is by minutes rather than by flights, so a few very long delays count for as much as many short ones.

Carrier
79%
National Airspace System
15%
Extreme weather
6%

The largest share of delay minutes, 79%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. Unlike weather, that is a management outcome, and it is the category where the gap between two carriers on the same schedule is genuinely earned. It accounts for 1,058 of the 1,333 delay minutes reported here. The split is drawn from 1,333 delay minutes reported on OO 4031.

Cancellations are rare at 0.29%, below the national 1.81% 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 1.2% land an hour or more behind schedule, against 8.1% 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. It is also long enough that the aircraft usually flies three or four legs a day rather than six, which slows how fast delay compounds.

OO 4031 is not only a SEA to ONT flight. It also flew ONT to SEA (321 flights, 89.7% 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. 347 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.

Other routes flown as OO 4031
Also flown as	Flights	On time	Avg delay	Cancelled	Grade
ONT to SEAthin sample	321	89.7%	64 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: 89.6% on time and 0.29% cancelled. That is a base rate, not a promise about any single day.

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