Route reliability record

ORD→SLC

Chicago to Salt Lake City

Flights: 3,198
Period: July 2025 to June 2026
Distance: 1,250 mi
Carriers: 5

This route sits in the middle of the pack with a C. About seven flights in ten arrive on time by the DOT's definition, 9 points worse than the national rate of 77.6%. The late ones land a little over an hour behind schedule. That rests on 3,198 flights, of which Delta Air Lines flew 1,011 at 71.8% on time.

Delta Air Lines is the most reliable of the three carriers covered here at 71.8% on time across 1,011 flights.

On time

68.8%

Arrivals under 15 minutes late, of 3,154 completed flights

Avg delay

79 min

Across delayed arrivals only, not all flights

Cancelled

1.16%

National rate is 1.81%

Best carrier

Delta

71.8% on time across 1,011 flights

These figures cover 3,198 flights between July 2025 and June 2026. Beyond the headline rate, 12.0% 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 SLC

The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 71.8% of the time; American Airlines manages 64.2%. Sample sizes sit next to every figure, because a two-point gap across 969 flights means less than a ten-point one.

On-time performance by carrier on ORD to SLC
Airline	Flights	On time	Avg delay	Cancelled	Grade
Delta Air Lines	1,011	71.8%	105 min	0.79%	C+
United Airlines	1,069	71.7%	64 min	0.84%	C+
American Airlines	969	64.2%	69 min	1.96%	D
Envoy Airthin sample	36	61.1%	48 min	0.00%	D+
SkyWest Airlinesthin sample	113	56.2%	87 min	0.88%	D+

Delta leads American by 8 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.

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 20 points, against 8 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am290 flights76.2%
8am–11am872 flights74.5%
11am–2pm697 flights72.8%
2pm–5pm350 flights68.7%
5pm–8pm591 flights60.4%
8pm–5am398 flights56.3%

Scale runs 50% to 80%. Rows with fewer than 30 flights show a dash.

The 8pm–5am window is where this operation falls apart: 56.3% on time, against 76.2% 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. The 8am–11am window is the busiest, with 872 flights scheduled in it.

Across the year

When delays peak on this route

This route's year swings by 23 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.September best, December worst

December is the weak month at 55.6% on time, against 79.0% in September. Winter delays cluster: a single storm system can account for most of a month's shortfall, so an average December hides both very good weeks and genuinely unflyable days. March was the busiest month here, with 316 flights.

Across the week, Tuesday is the strongest day at 76.6% on time and Sunday the weakest at 63.2%. 13 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 77,000 reported delay minutes.

Late-arriving aircraft
38%
Carrier
37%
National Airspace System
15%
Extreme weather
10%
Security
0%

38% 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 77,000 reported delay minutes here, that single category outweighs weather by 4 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 77,183 reported delay minutes.

The largest share of delay minutes, 37%, 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 28,000 of the 77,000 delay minutes reported here.

Cancellations sit at 1.16% against a national 1.81%, which is ordinary. Diversions add another 0.22%.

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. 12.0% of arrivals land a full hour or more behind schedule, against 8.1% 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.

The 1,250 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. It is also long enough that the aircraft usually flies three or four legs a day rather than six, which slows how fast delay compounds.

The return leg is a different operation and performs like one: it runs 75.3% on time across 3,198 flights, 7 points above this direction. Departure banks, aircraft rotations and the congestion at each end all differ, so scoring the two directions together would average away a real 7 points of difference.

The sample behind these figures is 3,198 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. September runs 79.0% on time and December 55.6%, a swing of 23 points. If the dates move at all, move them out of December before you think about anything else. 3,154 completed flights over 12 months sit behind that.

Common questions

ORD to SLC questions

How often is ORD to SLC delayed?

About one flight in three arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 31.2% of the 3,198 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 ORD to SLC?

Delta Air Lines leads at 71.8% on time across 1,011 flights. American Airlines is at the other end on 64.2%, a gap of 8 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 SLC?

The 5am–8am departure window is the strongest at 76.2% on time. The 8pm–5am window is the weakest at 56.3%, 20 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 December delays on ORD to SLC?

December is the weakest month at 55.6% on time, compared with 79.0% in September. Across the year that is 23 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. ORD to SLC and SLC 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, July 2025 to June 2026. Updated monthly. How this data is collected.

Key figures