Flight number record

OO 5821

SkyWest Airlines · Chicago to Milwaukee

Route: ORD → MKE
Departs: 09:25
Flights: 271
Period: July 2025 to June 2026

Historical statistics for July 2025 to June 2026, not live status. For today’s OO 5821, 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 5821 sits in the middle of the pack with a C−. Close to three flights in four arrive on time by the DOT's definition, 4 points worse than the national rate of 77.6%. The late ones land about an hour behind schedule. That rests on 271 flights, with a median arrival 6 minutes early.

The national on-time rate over the same period is 77.6%, so OO 5821 runs 4 points behind the country as a whole. Across a thousand flights that is about 43 extra late arrivals.

On time

73.3%

Arrivals under 15 minutes late, of 258 completed flights

Avg delay

58 min

Across delayed arrivals only, not all flights

Cancelled

4.06%

National rate is 1.81%

1 hour+ late

8.5%

National rate is 8.1%

These figures cover 271 flights between July 2025 and June 2026. Beyond the headline rate, 8.5% 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 5821 flies

OO 5821 flies ORD to MKE without a single fixed slot. Its most common scheduled departure was 09:25, used on 81 of 271 flights, with 08:54 (49 flights) and 09:07 (35 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.

Departs 09:2581 flights29.9%
Departs 08:5449 flights18.1%
Departs 09:0735 flights12.9%

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 09:25 departure sits in the 8am–11am window. Across every US flight scheduled in that window the on-time rate is 84.1%, and OO 5821 runs 11 points worse at 73.3%. 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 5821 next to ORD to MKE

Every carrier on ORD to MKE combined arrived on time 64.1% of the time across 5,201 flights, so OO 5821 is 9 points ahead of it. SkyWest flew 4,933 flights on the same city pair under all its flight numbers, including this one, and those ran 63.7% on time. Across its whole network SkyWest Airlines managed 79.0%, which this flight trails by 6 points.

OO 5821 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
OO 5821thin sample	271	73.3%	58 min	4.06%	C−
All SkyWest Airlines on ORD–MKE	4,933	63.7%	93 min	4.64%	D−
All carriers on ORD–MKE	5,201	64.1%	93 min	4.75%	D−
SkyWest Airlines, whole network	852,935	79.0%	88 min	1.77%	B

Across the year

OO 5821 quarter by quarter

OO 5821 did not run the same all year. Its best quarter was Jul–Sep 2025 at 81.6% on time and its weakest Jan–Mar 2026 at 65.4%, a swing of 16 points on roughly 90 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 202590 flights81.6%
Oct–Dec 202576 flights67.1%
Jan–Mar 202684 flights65.4%
Apr–Jun 202621 flights—

Scale runs 55% to 85%. Rows with fewer than 30 flights show a dash.

By weekday, OO 5821 did best on Thursday at 84.2% on time and worst on Monday at 62.2%. Each day rests on about 39 flights, so a gap of 22 points is worth noticing but could still narrow in another year.

Delay causes

Why OO 5821 runs late

One category carries most of the weight here. Carrier accounts for 59% of the 3,986 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
59%
Late-arriving aircraft
22%
National Airspace System
13%
Extreme weather
6%

The largest share of delay minutes, 59%, 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 2,358 of the 3,986 delay minutes reported here. The split is drawn from 3,986 delay minutes reported on OO 5821.

Cancellations run at 4.06%, against 1.81% 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

8.5% of arrivals land an hour or more late, close to the national 8.1%. That is the figure that decides a connection, and it says a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last about an hour, which a normal layover absorbs.

The same number turns up on three other city pairs in the data, including TUL to DEN (29), SFO to OMA (19) and MSO to DEN (17), but none flew often enough under OO 5821 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to ORD to MKE only.

One caution: this is a thin sample. 271 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 5821

For a booking, the cancellation rate is the figure to plan around on OO 5821: 4.06% of its 271 scheduled flights did not operate. A late arrival costs about an hour, 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