Flight number record

OO 5121

SkyWest Airlines · Eau Claire to Chicago

Route: EAU → ORD
Departs: 05:00
Flights: 363
Period: July 2025 to June 2026

Historical statistics for July 2025 to June 2026, not live status. For today’s OO 5121, 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 5121 lands a B−, 3 points better than the national rate of 77.6%. About one flight in five arrives 15 minutes late or worse, and those flights are late by about 2.5 hours on average. That is a workable record, not a spotless one. That rests on 363 flights, with a median arrival 8 minutes early.

On time

80.3%

Arrivals under 15 minutes late, of 346 completed flights

Avg delay

148 min

Across delayed arrivals only, not all flights

Cancelled

4.41%

National rate is 1.81%

1 hour+ late

9.5%

National rate is 8.1%

These figures cover 363 flights between July 2025 and June 2026. Beyond the headline rate, 9.5% 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 5121 flies

OO 5121 flies EAU to ORD without a single fixed slot. Its most common scheduled departure was 05:00, used on 229 of 363 flights, with 05:30 (92 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.

Departs 05:00229 flights63.1%
Departs 05:3092 flights25.3%

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 05:00 departure sits in the 5am–8am window. Across every US flight scheduled in that window the on-time rate is 89.3%, and OO 5121 runs 9 points worse at 80.3%. Early departures usually start with an aircraft that has not flown yet that day, which is most of why the window does well.

Against the route

OO 5121 next to EAU to ORD

Every carrier on EAU to ORD combined arrived on time 71.8% of the time across 624 flights, so OO 5121 is 9 points ahead of it. Across its whole network SkyWest Airlines managed 79.0%, close to this flight's figure.

OO 5121 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
OO 5121thin sample	363	80.3%	148 min	4.41%	B−
All SkyWest Airlines on EAU–ORD	624	71.8%	126 min	4.65%	C−
All carriers on EAU–ORD	624	71.8%	126 min	4.65%	C−
SkyWest Airlines, whole network	852,935	79.0%	88 min	1.77%	B

Across the year

OO 5121 quarter by quarter

OO 5121 did not run the same all year. Its best quarter was Jul–Sep 2025 at 91.2% on time and its weakest Jan–Mar 2026 at 64.6%, a swing of 27 points on roughly 91 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 202592 flights91.2%
Oct–Dec 202592 flights83.7%
Jan–Mar 202688 flights64.6%
Apr–Jun 202691 flights80.5%

Scale runs 55% to 95%. Rows with fewer than 30 flights show a dash.

By weekday, OO 5121 did best on Monday at 89.6% on time and worst on Saturday at 70.0%. Each day rests on about 52 flights, so a gap of 20 points is worth noticing but could still narrow in another year.

Delay causes

Why OO 5121 runs late

One category carries most of the weight here. Carrier accounts for 62% of the 10,000 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
62%
Late-arriving aircraft
20%
Extreme weather
10%
National Airspace System
8%

The largest share of delay minutes, 62%, 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 6,212 of the 10,000 delay minutes reported here. The split is drawn from 10,086 delay minutes reported on OO 5121.

Cancellations run at 4.41%, against 1.81% nationally. That is roughly one flight in 25 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. 9.5% 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 one other city pair in the data, including ORD to DEC (60), but none flew often enough under OO 5121 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to EAU to ORD only.

One caution: this is a thin sample. 363 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 5121

For a booking, the cancellation rate is the figure to plan around on OO 5121: 4.41% of its 363 scheduled flights did not operate. A late arrival costs about 2.5 hours, 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