Flight number record

OO 4027

SkyWest Airlines · Seattle to Ontario

Route: SEA → ONT
Departs: 19:55
Flights: 280
Period: July 2025 to June 2026

Historical statistics for July 2025 to June 2026, not live status. For today’s OO 4027, 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 4027 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 11 points better than the national rate of 77.6%. When something does go wrong the average delay runs roughly 55 minutes. That rests on 280 flights, with a median arrival 9 minutes early.

Set against the rest of the country, OO 4027's record is 11 points better than the US average of 77.6%. That gap is worth roughly 113 fewer late arrivals for every thousand flights.

On time

88.9%

Arrivals under 15 minutes late, of 279 completed flights

Avg delay

53 min

Across delayed arrivals only, not all flights

Cancelled

0.36%

National rate is 1.81%

1 hour+ late

2.9%

National rate is 8.1%

These figures cover 280 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 4027 flies

OO 4027 flies SEA to ONT without a single fixed slot. Its most common scheduled departure was 19:55, used on 99 of 280 flights, with 19:50 (92 flights) and 20:05 (39 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.

Departs 19:5599 flights35.4%
Departs 19:5092 flights32.9%
Departs 20:0539 flights13.9%

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 19:55 departure sits in the 5pm–8pm window. Across every US flight scheduled in that window the on-time rate is 68.2%, and OO 4027 runs 21 points better at 88.9%. By that time of day most aircraft have flown several legs already, and whatever went wrong earlier is still in the schedule.

Against the route

OO 4027 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 4027 is 6 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 10 points.

OO 4027 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
OO 4027thin sample	280	88.9%	53 min	0.36%	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 4027 quarter by quarter

Quarter by quarter OO 4027 held fairly steady: 88.0% in Jul–Sep 2025, 89.7% in Oct–Dec 2025 and 88.6% in Jan–Mar 2026. A spread of 2 points is about what a sample of this size moves on its own, so the annual figure is a fair summary.

Jul–Sep 202592 flights88.0%
Oct–Dec 202587 flights89.7%
Jan–Mar 202689 flights88.6%
Apr–Jun 202612 flights—

Scale runs 80% to 95%. Rows with fewer than 30 flights show a dash.

By weekday, OO 4027 did best on Saturday at 97.6% on time and worst on Friday at 74.4%. Each day rests on about 40 flights, so a gap of 23 points is worth noticing but could still narrow in another year.

Delay causes

Why OO 4027 runs late

One category carries most of the weight here. Carrier accounts for 83% of the 1,630 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
83%
National Airspace System
10%
Extreme weather
7%

The largest share of delay minutes, 83%, 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 1,355 of the 1,630 delay minutes reported here. The split is drawn from 1,630 delay minutes reported on OO 4027.

Cancellations are rare at 0.36%, 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 2.9% 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.

The same number turns up on four other city pairs in the data, including FSD to MSP (31), CLE to DTW (21) and IND to AUS (20), but none flew often enough under OO 4027 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to SEA to ONT only.

One caution: this is a thin sample. 280 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 4027

For a booking, OO 4027 has one of the better records a US domestic flight can show: 88.9% on time and 0.36% 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