Flight number record
OO 5121
SkyWest Airlines · Eau Claire to Chicago
- Route
- EAU → ORD
- Departs
- 05:00
- Flights
- 357
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 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 77.3%. About one flight in five arrives 15 minutes late or worse, and those flights are late by about 2.4 hours on average. That rests on 357 flights, with a median arrival 9 minutes early.
Key figures
On time
80.1%
Arrivals under 15 minutes late, of 341 completed flights
Avg delay
143 min
Across delayed arrivals only, not all flights
Cancelled
4.20%
National rate is 1.89%
1 hour+ late
9.7%
National rate is 8.3%
These figures cover 357 flights between September 2025 and August 2026. Beyond the headline rate, 9.7% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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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 285 of 357 flights.
- Departs 05:00285 flights79.8%
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 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 80.1%. Early departures usually start with an aircraft that has not flown yet that day, which is most of why the window does well.
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Against the route
OO 5121 next to EAU to ORD
Every carrier on EAU to ORD combined arrived on time 70.9% of the time across 625 flights, so OO 5121 is 9 points ahead of it. Across its whole network SkyWest Airlines managed 78.7%, close to this flight's figure.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| OO 5121thin sample | 357 | 80.1% | 143 min | 4.20% | B− |
| All SkyWest Airlines on EAU–ORD | 625 | 70.9% | 125 min | 4.64% | C− |
| All carriers on EAU–ORD | 625 | 70.9% | 125 min | 4.64% | C− |
| SkyWest Airlines, whole network | 855,406 | 78.7% | 88 min | 1.79% | 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 93.3% on time and its weakest Jan–Mar 2026 at 64.6%, a swing of 29 points on roughly 71 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 flights93.3%
- Oct–Dec 202592 flights83.7%
- Jan–Mar 202688 flights64.6%
- Apr–Jun 202691 flights80.5%
- Jul–Sep 202656 flights89.3%
Scale runs 55% to 100%.
By weekday, OO 5121 did best on Monday at 89.8% on time and worst on Saturday at 70.0%. Each day rests on about 51 flights, so a gap of 20 points is worth noticing but could still narrow in another year.
Arrival by arrival
How late OO 5121 runs when it is late
OO 5121 often beats the schedule: 137 of 341 completed flights, 40%, arrived 15 minutes or more early. The 68 late arrivals split 24 under half an hour, 11 between 30 and 60 minutes, and 33 an hour or more.
- 15+ min early137 flights40.2%
- Within 15 min136 flights39.9%
- 15–29 min late24 flights7.0%
- 30–59 min late11 flights3.2%
- 1–2 hours late9 flights2.6%
- 2+ hours late24 flights7.0%
Scale runs 0% to 100%.
Share of 341 completed flights by arrival against schedule.
7 of 58 late departures made up the time and arrived on time, 12% of them. 17 flights left on time and still arrived late.
The worst days
Worst days for OO 5121
The latest arrival of the period was on 26 April 2026, 10 hours 27 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). The same cause led on three of the five worst days.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 26 April 2026 | 10 hours 27 minutes | Carrier |
| 3 December 2025 | 9 hours 34 minutes | Late-arriving aircraft |
| 6 March 2026 | 8 hours 51 minutes | Carrier |
| 19 October 2025 | 8 hours 50 minutes | Late-arriving aircraft |
| 8 February 2026 | 8 hours 13 minutes | Carrier |
Delay causes
Why OO 5121 runs late
Carrier accounts for 62% of the 9,698 delay minutes carriers reported here, and the remaining four split what is left.
- 62%Carrier
- 20%Late-arriving aircraft
- 11%Extreme weather
- 7%National Airspace System
Extreme weather accounts for 11% of delay minutes, well above the single-digit share typical across the system. Weather delays are lumpy: they arrive as whole bad days rather than as a steady drag, so the quarterly figures above are the more useful view of the risk. The national share is 6%, so this operation carries roughly 1.8 times the usual weather exposure. The split is drawn from 9,698 delay minutes reported on OO 5121.
Cancellations run at 4.20%, against 1.89% nationally. That is about 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
9.7% of arrivals land a full hour or more behind schedule, against 8.3% nationally. Ninety minutes is the honest minimum for a connection 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 (96), 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. 357 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: 4.20% of its 357 scheduled flights did not operate. A late arrival costs about 2.4 hours, but a cancellation costs the day, so leave a later option open.
Related
Where to go next
- Chicago O'Hare International (ORD) 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
- How often a connection fails at the major US hubs
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.