Route reliability record

LAS→ORD

Las Vegas to Chicago

Flights: 5,297
Period: July 2025 to June 2026
Distance: 1,514 mi
Carriers: 5

This route lands a B, about a point worse than the national rate of 77.6%. About one flight in four arrive 15 minutes late or worse, and those flights are late by a little over an hour on average. That is a workable record, not a spotless one. That rests on 5,297 flights, of which United Airlines flew 2,330 at 79.3% on time.

United Airlines is the most reliable of the three carriers covered here at 79.3% on time across 2,330 flights.

On time

76.5%

Arrivals under 15 minutes late, of 5,193 completed flights

Avg delay

79 min

Across delayed arrivals only, not all flights

Cancelled

1.25%

National rate is 1.81%

Best carrier

United

79.3% on time across 2,330 flights

These figures cover 5,297 flights between July 2025 and June 2026. Beyond the headline rate, 8.3% 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.

Carrier by carrier

Which airline is most reliable on LAS to ORD

The choice of carrier is not cosmetic here. United Airlines arrives on time 79.3% of the time; Southwest Airlines manages 66.6%. Sample sizes sit next to every figure, because a two-point gap across 669 flights means less than a ten-point one.

On-time performance by carrier on LAS to ORD
Airline	Flights	On time	Avg delay	Cancelled	Grade
Spirit Airlinesthin sample	266	83.6%	54 min	1.50%	B
United Airlines	2,330	79.3%	71 min	0.43%	B+
American Airlines	1,848	76.2%	99 min	2.27%	B
Frontier Airlinesthin sample	184	68.6%	88 min	4.35%	C−
Southwest Airlines	669	66.6%	58 min	0.30%	C+

The spread between United and Southwest is 13 points, wide enough that it should decide the booking. On a hundred trips that is 13 more arrivals inside the on-time window.

Departure window

The best time of day to leave

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 23 points, against 13 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am783 flights90.0%
8am–11am1,126 flights80.8%
11am–2pm827 flights67.7%
2pm–5pm1,004 flights66.9%
5pm–8pm644 flights71.3%
8pm–5am913 flights81.7%

Scale runs 60% to 95%. Rows with fewer than 30 flights show a dash.

Book the early departure. Flights leaving between 5am–8am arrive on time 90.0% of the time, against 66.9% for the afternoon window. That is 23 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 8am–11am window is the busiest, with 1,126 flights scheduled in it.

Across the year

When delays peak on this route

This route's year swings by 13 points from best month to worst, which is wide. An annual average tells you very little about the week you are actually flying, so read the strip rather than the headline if your dates are fixed.

Darker means more delays. Figures are on-time percentages.February best, July worst

July is the worst month at 71.0% on time, 13 points below February, the best at 84.3%. Summer afternoon convection and peak-season schedules land on the same weeks every year, so this is a pattern you can book around rather than a run of bad luck. April was the busiest month here, with 504 flights.

Across the week, Tuesday is the strongest day at 83.3% on time and Friday the weakest at 72.3%. 11 points is a smaller lever than departure hour, but it is free.

Delay causes

Why this route gets delayed

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 96,000 reported delay minutes.

Late-arriving aircraft
42%
National Airspace System
30%
Carrier
27%
Extreme weather
2%

42% 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 96,000 reported delay minutes here, that single category outweighs weather by 28 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 95,919 reported delay minutes.

The practical consequence: the 5am–8am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 90.0% on time here.

Cancellations sit at 1.25% against a national 1.81%, which is ordinary. Diversions add another 0.72%.

Connections and stage length

What a delay here actually costs

8.3% 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 are the a little over an hour kind, which a normal layover absorbs.

At 1,514 miles this is transcontinental flying, and long routes get a quiet structural advantage. Scheduled block time on a flight this length carries more padding in absolute minutes, so a twenty-minute late departure often still becomes an on-time arrival. Read the on-time rate here as slightly flattering next to a short-haul route with the same operational quality.

The return leg runs 73.7% on time across 5,297 flights, within 3 points of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.

The sample behind these figures is 5,297 flights, enough that the headline rate is stable to within roughly a point. The hour-block and month splits divide that further, so read the thinner bars with more caution than the headline.

What to do with this

Booking this route

Put together: the calendar is the biggest lever here, not the carrier or the hour. February runs 84.3% on time and July 71.0%, a swing of 13 points. If the dates move at all, move them out of July before you think about anything else. 5,193 completed flights over 12 months sit behind that.

Common questions

LAS to ORD questions

How often is LAS to ORD delayed?

About one flight in four arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 23.5% of the 5,297 flights in this analysis, against 22.4% nationally. Delayed flights are late by a little over an hour on average.

Which airline is most reliable on LAS to ORD?

United Airlines leads at 79.3% on time across 2,330 flights. Southwest Airlines is at the other end on 66.6%, a gap of 13 points. Sample size matters as much as the percentage: a rate built from a few hundred flights moves around far more than one built from ten thousand.

What time of day has the fewest delays on LAS to ORD?

The 5am–8am departure window is the strongest at 90.0% on time. The 2pm–5pm window is the weakest at 66.9%, 23 points behind. Later departures inherit delays from earlier flights the same aircraft has already flown, which is why the curve slopes the way it does.

How bad are July delays on LAS to ORD?

July is the weakest month at 71.0% on time, compared with 84.3% in February. Across the year that is 13 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.

Where to go next

Direction matters. LAS to ORD and ORD to LAS are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.

Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Updated monthly. How this data is collected.

Key figures