Route reliability record
ORD→LAS
Chicago to Las Vegas
- Flights
- 5,367
- Period
- June 2025 to May 2026
- Distance
- 1,514 mi
- Carriers
- 5
This route sits in the middle of the pack with a C. Close to three flights in four arrive on time by the DOT's definition, 3 points worse than the national rate of 77.4%. The late ones land a little over an hour behind schedule. That rests on 5,367 flights, of which United Airlines flew 2,330 at 79.8% on time.
United Airlines is the most reliable of the three carriers covered here at 79.8% on time across 2,330 flights.
Key figures
On time
74.1%
Arrivals under 15 minutes late, of 5,284 completed flights
Avg delay
71 min
Across delayed arrivals only, not all flights
Cancelled
1.19%
National rate is 1.80%
Best carrier
United
79.8% on time across 2,330 flights
These figures cover 5,367 flights between June 2025 and May 2026. Beyond the headline rate, 9.6% 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 ORD to LAS
The choice of carrier is not cosmetic here. United Airlines arrives on time 79.8% of the time; American Airlines manages 67.6%. Sample sizes sit next to every figure, because a two-point gap across 1,820 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Spirit Airlinesthin sample | 320 | 81.3% | 73 min | 1.25% | B |
| United Airlines | 2,330 | 79.8% | 62 min | 0.39% | B+ |
| Southwest Airlines | 723 | 72.2% | 69 min | 0.69% | C+ |
| American Airlines | 1,820 | 67.6% | 73 min | 1.98% | C |
| Frontier Airlinesthin sample | 174 | 57.3% | 118 min | 5.75% | D− |
The spread between United and American is 12 points, wide enough that it should decide the booking. On a hundred trips that is 12 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 33 points, against 12 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am1,118 flights90.2%
- 8am–11am914 flights78.8%
- 11am–2pm958 flights80.6%
- 2pm–5pm728 flights67.7%
- 5pm–8pm821 flights60.9%
- 8pm–5am828 flights57.6%
Scale runs 50% to 95%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is where this operation falls apart: 57.6% on time, against 90.2% for the 5am–8am slot. By evening the aircraft flying these rotations have absorbed a full day of small delays and there is no slack left to recover in.
Across the year
When delays peak on this route
This route's year swings by 18 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.
Delays peak in April, when the on-time rate falls to 64.5%. February is the strongest month at 82.6%. Moving a flexible trip across that boundary buys 18 points.
Across the week, Tuesday is the strongest day at 79.2% on time and Sunday the weakest at 68.2%. 11 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 46% of the 97,000 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.
- 46%Late-arriving aircraft
- 29%Carrier
- 19%National Airspace System
- 5%Extreme weather
- 0%Security
46% 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 97,000 reported delay minutes here, that single category outweighs weather by 8 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 90.2% on time here.
Cancellations sit at 1.19% against a national 1.80%, which is ordinary. Diversions add another 0.35%.
Connections and stage length
What a delay here actually costs
For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 9.6% of arrivals land a full hour or more behind schedule, against 8.2% nationally. A 45-minute layover does not survive that, and no amount of walking quickly changes it. Ninety minutes is the honest minimum here, and two hours if the onward flight is on a separate ticket.
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 76.7% on time across 5,368 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 5,367 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 82.6% on time and April 64.5%, a swing of 18 points. If the dates move at all, move them out of April before you think about anything else.
Common questions
ORD to LAS questions
How often is ORD to LAS 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 25.9% of the 5,367 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 ORD to LAS?
United Airlines leads at 79.8% on time across 2,330 flights. American Airlines is at the other end on 67.6%, a gap of 12 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 ORD to LAS?
The 5am–8am departure window is the strongest at 90.2% on time. The 8pm–5am window is the weakest at 57.6%, 33 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 April delays on ORD to LAS?
April is the weakest month at 64.5% on time, compared with 82.6% in February. Across the year that is 18 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
- LAS to ORD — the return legseparate record
- Chicago O'Hare International (ORD) delay statistics
- Harry Reid International (LAS) delay statistics
- Spirit Airlines on-time record81.3%
- United Airlines on-time record79.8%
- Southwest Airlines on-time record72.2%
- 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. ORD to LAS and LAS to ORD 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.