Carrier route record

DLIAD→SLC

Delta Air Lines · Washington to Salt Lake City

Flights: 364
Period: July 2025 to June 2026
Share of route: 51%
Carriers: 2

Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Delta Air Lines.

Delta on IAD to SLC earns a B. More than four flights in five arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 7 points better than the national rate of 77.6%. When something does go wrong the average delay runs close to two hours. That rests on 364 flights, with a median arrival 5 minutes early.

Set against the rest of the country, Delta's IAD to SLC record is 7 points better than the US average of 77.6%. That gap is worth roughly 65 fewer late arrivals for every thousand flights.

On time

84.1%

Arrivals under 15 minutes late, of 358 completed flights

Avg delay

101 min

Across delayed arrivals only, not all flights

Cancelled

1.65%

National rate is 1.81%

Whole route

84.0%

Every carrier on IAD to SLC, 714 flights

These figures cover 364 flights between July 2025 and June 2026. The median arrival is 5 minutes early, which is the part an average hides: most flights here are fine, and the on-time rate is decided by a tail of badly late ones. On-time means under 15 minutes late, the DOT's own threshold.

Carrier by carrier

Delta against every carrier on IAD to SLC

Delta flew 364 of the 714 flights on IAD to SLC, most of the route. Its 84.1% on time is about level with the route as a whole at 84.0%. Ranked by on-time rate it is first of two carriers on the route, where the range runs from Delta at 84.1% to United at 83.9%. One 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 IAD to SLC
Airline	Flights	On time	Avg delay	Cancelled	Grade
Delta Air Lines (this page)thin sample	364	84.1%	101 min	1.65%	B
United Airlinesthin sample	350	83.9%	83 min	0.57%	B+

Flight by flight

Delta flight numbers on IAD to SLC

DL 43207:0584.1% · 364 flights

Departure window

When Delta runs best on this route

Departure time is the single lever a traveller controls, and it moves the odds more than most people expect. Each bar below is the on-time rate for flights scheduled to leave inside that window, across 364 flights.

There are not enough flights in each departure window to split Delta's IAD to SLC record by time of day without the percentages moving on noise. The headline rate of 84.1% is the reliable figure here.

Across the year

Delta on IAD to SLC through the year

Darker means more delays. Figures are on-time percentages.May best, December worst

December is the weak month at 70.0% on time, against 93.5% in May. 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 31 flights.

Across the week, Monday is the strongest day at 89.8% on time and Saturday the weakest at 80.8%. 9 points is a smaller lever than departure hour, but it is free.

Delay causes

Why Delta runs late on this route

One category carries most of the weight here. Carrier accounts for 83% of the 5,748 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.

Carrier
83%
National Airspace System
14%
Extreme weather
2%

The largest share of delay minutes, 83%, 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 4,799 of the 5,748 delay minutes reported here. The split is drawn from 5,748 reported delay minutes.

Cancellations sit at 1.65% against a national 1.81%, which is ordinary. Diversions add another 0.00%.

Connections and stage length

What a delay here costs

6.1% 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 last close to two hours, which a normal layover absorbs.

At 1,827 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 86.0% on time across 364 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. 364 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 Delta on IAD to SLC

Put together: treat all of this as provisional. 364 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 84.1% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 358 completed flights over 12 months sit behind that.

Where to go next

Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.

Key figures