Route reliability record
LAS→ORD
Las Vegas to Chicago
- Flights
- 5,368
- Period
- June 2025 to May 2026
- Distance
- 1,514 mi
- Carriers
- 5
This route lands a B, level with the national rate of 77.4%. 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 5,368 flights, of which United Airlines flew 2,332 at 80.0% on time.
United Airlines is the most reliable of the three carriers covered here at 80.0% on time across 2,332 flights.
Key figures
On time
76.7%
Arrivals under 15 minutes late, of 5,269 completed flights
Avg delay
77 min
Across delayed arrivals only, not all flights
Cancelled
1.14%
National rate is 1.80%
Best carrier
United
80.0% on time across 2,332 flights
These figures cover 5,368 flights between June 2025 and May 2026. Beyond the headline rate, 8.2% 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 80.0% of the time; Southwest Airlines manages 67.4%. Sample sizes sit next to every figure, because a two-point gap across 723 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Spirit Airlinesthin sample | 324 | 83.8% | 54 min | 1.23% | B |
| United Airlines | 2,332 | 80.0% | 68 min | 0.43% | B+ |
| American Airlines | 1,817 | 75.6% | 96 min | 2.04% | B |
| Frontier Airlinesthin sample | 172 | 67.5% | 87 min | 4.65% | C− |
| Southwest Airlines | 723 | 67.4% | 58 min | 0.28% | 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 26 points, against 13 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am813 flights91.3%
- 8am–11am1,164 flights81.2%
- 11am–2pm835 flights66.3%
- 2pm–5pm983 flights65.7%
- 5pm–8pm708 flights72.6%
- 8pm–5am865 flights82.4%
Scale runs 55% to 95%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 91.3% of the time, against 65.7% for the afternoon window. That is 26 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on.
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.
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.
Across the week, Tuesday is the strongest day at 82.1% on time and Monday the weakest at 71.9%. 10 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
One category carries most of the weight here. Late-arriving aircraft accounts for 42% of the 94,000 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.
- 42%Late-arriving aircraft
- 29%National Airspace System
- 27%Carrier
- 2%Extreme weather
- 0%Security
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 94,000 reported delay minutes here, that single category outweighs weather by 25 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 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 91.3% on time here.
Cancellations sit at 1.14% against a national 1.80%, which is ordinary. Diversions add another 0.71%.
Connections and stage length
What a delay here actually costs
8.2% of arrivals land an hour or more late, close to the national 8.2%. 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 74.1% on time across 5,367 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 5,368 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.
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 23.3% of the 5,368 flights in this analysis, against 22.6% 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 80.0% on time across 2,332 flights. Southwest Airlines is at the other end on 67.4%, 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 91.3% on time. The 2pm–5pm window is the weakest at 65.7%, 26 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.
Related
Where to go next
- ORD to LAS — the return legseparate record
- Harry Reid International (LAS) delay statistics
- Chicago O'Hare International (ORD) delay statistics
- Spirit Airlines on-time record83.8%
- United Airlines on-time record80.0%
- American Airlines on-time record75.6%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.05 million flight records
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, June 2025 to May 2026. Updated monthly. How this data is collected.