Flight number record

OO 5539

SkyWest Airlines · Arcata/Eureka to San Francisco

Route: ACV → SFO
Departs: 15:50
Flights: 274
Period: July 2025 to June 2026

Historical statistics for July 2025 to June 2026, not live status. For today’s OO 5539, 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 5539 lands a B, about a point worse than the national rate of 77.6%. About one flight in four arrives 15 minutes late or worse, and those flights are late by an hour and a half on average. That is a workable record, not a spotless one. That rests on 274 flights, with a median arrival 12 minutes early.

On time

76.6%

Arrivals under 15 minutes late, of 265 completed flights

Avg delay

84 min

Across delayed arrivals only, not all flights

Cancelled

2.92%

National rate is 1.81%

1 hour+ late

9.8%

National rate is 8.1%

These figures cover 274 flights between July 2025 and June 2026. Beyond the headline rate, 9.8% 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 5539 flies

OO 5539 flies ACV to SFO without a single fixed slot. Its most common scheduled departure was 15:50, used on 53 of 274 flights, with 16:10 (49 flights) and 15:55 (49 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.

Departs 15:5053 flights19.3%
Departs 16:1049 flights17.9%
Departs 15:5549 flights17.9%

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 15:50 departure sits in the 2pm–5pm window. Across every US flight scheduled in that window the on-time rate is 72.4%, and OO 5539 runs 4 points better at 76.6%. Midday slots inherit some of the morning's delays without yet carrying the full weight of the evening's.

Against the route

OO 5539 next to ACV to SFO

Every carrier on ACV to SFO combined arrived on time 63.8% of the time across 1,283 flights, so OO 5539 is 13 points ahead of it. Across its whole network SkyWest Airlines managed 79.0%, which this flight trails by 2 points.

OO 5539 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
OO 5539thin sample	274	76.6%	84 min	2.92%	B
All SkyWest Airlines on ACV–SFO	1,283	63.8%	87 min	2.96%	D
All carriers on ACV–SFO	1,283	63.8%	87 min	2.96%	D
SkyWest Airlines, whole network	852,935	79.0%	88 min	1.77%	B

Across the year

OO 5539 quarter by quarter

OO 5539 did not run the same all year. Its best quarter was Jul–Sep 2025 at 84.1% on time and its weakest Apr–Jun 2026 at 48.7%, a swing of 35 points on roughly 69 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 202569 flights84.1%
Oct–Dec 202591 flights79.1%
Jan–Mar 202673 flights81.7%
Apr–Jun 202641 flights48.7%

Scale runs 40% to 90%. Rows with fewer than 30 flights show a dash.

By weekday, OO 5539 did best on Friday at 85.7% on time and worst on Sunday at 66.7%. Each day rests on about 39 flights, so a gap of 19 points is worth noticing but could still narrow in another year.

Delay causes

Why OO 5539 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 5,223 reported delay minutes.

Late-arriving aircraft
34%
National Airspace System
28%
Carrier
27%
Extreme weather
10%

34% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. That is a cascade, and cascades start small and grow through the day. Across 5,223 reported delay minutes here, that single category outweighs weather by 4 to one. It is the strongest argument for booking the first departure of the morning, when the aircraft has been sitting at the gate overnight with nothing to inherit. The split is drawn from 5,223 delay minutes reported on OO 5539.

Cancellations run at 2.92%, against 1.81% nationally. That is roughly one flight in 30 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. 9.8% 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 six other city pairs in the data, including PIA to DEN (23), SAV to ORD (6) and ORD to MLI (6), but none flew often enough under OO 5539 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to ACV to SFO only.

One caution: this is a thin sample. 274 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 5539

For a booking, the cancellation rate is the figure to plan around on OO 5539: 2.92% of its 274 scheduled flights did not operate. A late arrival costs an hour and a half, 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