Carrier route record

UABOI→ORD

United Airlines · Boise to Chicago

Flights: 244
Period: September 2025 to August 2026
Share of route: 22%
Carriers: 4

Historical statistics for September 2025 to August 2026, not live status. For today’s flights, check with United Airlines.

United on BOI to ORD sits in the middle of the pack with a B+. Close to three flights in four arrive on time by the DOT's definition, 2 points worse than the national rate of 77.3%. The late ones land an hour and a half behind schedule. That rests on 244 flights, with a median arrival 1 minute early.

The US average over the same twelve months is 77.3%, so there is little to separate United on BOI to ORD from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.

On time

75.5%

Arrivals under 15 minutes late, of 241 completed flights

Avg delay

91 min

Across delayed arrivals only, not all flights

Cancelled

0.82%

National rate is 1.89%

Whole route

74.9%

Every carrier on BOI to ORD, 1,111 flights

These figures cover 244 flights between September 2025 and August 2026. Beyond the headline rate, 11.6% of arrivals land a full hour or more behind schedule, against 8.3% nationally.

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Carrier by carrier

United against every carrier on BOI to ORD

United flew 244 of the 1,111 flights on BOI to ORD, about 22% of it. Its 75.5% on time is about level with the route as a whole at 74.9%. Ranked by on-time rate it is number two of four carriers on the route, where the range runs from SkyWest at 82.9% to American at 63.5%. Two of those carriers flew fewer than 365 flights here, so treat their positions as rough.

Only one carrier clears this site's 365-flight floor here, so there is no comparison to draw. The table below is the full picture.

On-time performance by carrier on BOI to ORD
Airline	Flights	On time	Avg delay	Cancelled	Grade
SkyWest Airlines	507	82.9%	78 min	2.17%	B
United Airlines (this page)thin sample	244	75.5%	91 min	0.82%	B+
Envoy Airthin sample	152	63.8%	111 min	0.00%	D+
American Airlinesthin sample	208	63.5%	102 min	0.00%	D+

Timetable by Aviasales, a Travelpayouts partner. Booking through it may earn this site a commission at no cost to you; it changes no figure here.

Departure window

When United runs best on this route

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 23 points, against half a point between the best and worst carrier.

5am–8am—
8am–11am50 flights94.0%
11am–2pm193 flights71.1%
2pm–5pm1 flights—
5pm–8pm—
8pm–5am—

Scale runs 65% to 100%. Rows with fewer than 30 flights show a dash.

The weak window here is the middle of the day, not the evening: 11am–2pm runs 71.1% on time against 94.0% for 8am–11am. That shape usually means a departure bank rather than an accumulating delay, so the recovery later in the afternoon is real rather than noise. The 11am–2pm window is the busiest, with 193 flights scheduled in it.

Across the year

United on BOI to ORD through the year

Jul–Sep 202535 flights74.3%
Oct–Dec 202586 flights83.5%
Apr–Jun 202661 flights78.3%
Jul–Sep 202662 flights62.3%

Scale runs 55% to 90%.

Monthly volumes are too low here to break the year into twelve reliable readings. What the twelve-month total says is 75.5% on time across 244 flights.

United on BOI to ORD did not run the same all year. Its best quarter was Oct–Dec 2025 at 83.5% on time and its weakest Jul–Sep 2026 at 62.3%, a swing of 21 points on roughly 61 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.

Across the week, Tuesday is the strongest day at 88.2% on time and Friday the weakest at 65.7%, a spread of 23 points.

Arrival by arrival

How late United on BOI to ORD runs when it is late

The 59 late arrivals split 24 under half an hour, 7 between 30 and 60 minutes, and 28 an hour or more.

15+ min early53 flights22.0%
Within 15 min129 flights53.5%
15–29 min late24 flights10.0%
30–59 min late7 flights2.9%
1–2 hours late13 flights5.4%
2+ hours late15 flights6.2%

Scale runs 0% to 100%.

Share of 241 completed flights by arrival against schedule.

6 of 45 late departures made up the time and arrived on time, 13% of them. In the other direction, 20 flights left on time yet arrived 15 minutes late or more, so that delay built up after pushback: in the air, in a holding pattern or on the ground at ORD.

The worst days

Worst days for United on BOI to ORD

The latest arrival of the period was on 22 May 2026, 7 hours 11 minutes behind schedule; most of its delay minutes were filed as a late-arriving aircraft. On four of the five worst days the largest share was filed as national airspace system delay.

The latest arrivals of United on BOI to ORD in the period
Date	Arrived late by	Largest filed cause
22 May 2026	7 hours 11 minutes	Late-arriving aircraft
27 July 2026	6 hours 21 minutes	National Airspace System
31 August 2026	5 hours 15 minutes	National Airspace System
10 November 2025	5 hours	National Airspace System
10 June 2026	4 hours 23 minutes	National Airspace System

Delay causes

Why United runs late on this route

National Airspace System accounts for 53% of the 5,363 delay minutes carriers reported here, and the remaining four split what is left.

National Airspace System
53%
Late-arriving aircraft
40%
Carrier
7%
Extreme weather
0%

40% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 5,363 reported delay minutes here, that single category outweighs weather by 40 to one. The split is drawn from 5,363 reported delay minutes.

53% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 2,849 minutes out of 5,363, against a national NAS share of 21%.

Cancellations are rare at 0.82%, below the national 1.89% 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 stage length

What a delay here costs

11.6% 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 1,437 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.

The return leg runs 77.4% on time across 245 flights, within 2 points of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.

One caution: this is a thin sample. 244 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 United on BOI to ORD

Put together: treat all of this as provisional. 244 flights over twelve months is enough to clear this site's floor and not enough to be confident to better than a couple of points. The 75.5% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 241 completed flights over 12 months sit behind that.

Where to go next

Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated 22 October 2026; recomputed monthly. How this data is collected.

Key figures