Carrier route record
UAIAD→SLC
United Airlines · Washington to Salt Lake City
- Flights
- 350
- Period
- July 2025 to June 2026
- Share of route
- 49%
- Carriers
- 2
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with United Airlines.
United on IAD to SLC lands a B+, 6 points better than the national rate of 77.6%. About one flight in six arrives 15 minutes late or worse, and those flights are late by an hour and a half on average. That is a workable record, not a spotless one. That rests on 350 flights, with a median arrival 10 minutes early.
Set against the rest of the country, United's IAD to SLC record is 6 points better than the US average of 77.6%. That gap is worth roughly 63 fewer late arrivals for every thousand flights.
Key figures
On time
83.9%
Arrivals under 15 minutes late, of 347 completed flights
Avg delay
83 min
Across delayed arrivals only, not all flights
Cancelled
0.57%
National rate is 1.81%
Whole route
84.0%
Every carrier on IAD to SLC, 714 flights
These figures cover 350 flights between July 2025 and June 2026. The median arrival is 10 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
United against every carrier on IAD to SLC
United flew 350 of the 714 flights on IAD to SLC, about 49% of it. Its 83.9% on time is about level with the route as a whole at 84.0%. Ranked by on-time rate it is last 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.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Delta Air Linesthin sample | 364 | 84.1% | 101 min | 1.65% | B |
| United Airlines (this page)thin sample | 350 | 83.9% | 83 min | 0.57% | B+ |
Flight by flight
United flight numbers on IAD to SLC
Departure window
When United 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 350 flights.
- 5am–8am—
- 8am–11am49 flights91.8%
- 11am–2pm—
- 2pm–5pm—
- 5pm–8pm301 flights82.6%
- 8pm–5am—
Scale runs 75% to 95%. Rows with fewer than 30 flights show a dash.
Book the morning departure. Flights leaving between 8am–11am arrive on time 91.8% of the time, against 82.6% for the evening window. That is 9 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 5pm–8pm window is the busiest, with 301 flights scheduled in it.
Across the year
United on IAD to SLC through the year
Delays peak in November, when the on-time rate falls to 80.0%. August is the strongest month at 93.8%. Moving a flexible trip across that boundary buys 14 points. August was the busiest month here, with 32 flights.
Across the week, Tuesday is the strongest day at 90.0% on time and Thursday the weakest at 76.0%. 14 points is a smaller lever than departure hour, but it is free.
Delay causes
Why United runs late on this route
One category carries most of the weight here. Late-arriving aircraft accounts for 55% of the 4,637 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.
- 55%Late-arriving aircraft
- 29%Carrier
- 14%National Airspace System
- 2%Extreme weather
55% 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 4,637 reported delay minutes here, that single category outweighs weather by 36 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 4,637 reported delay minutes.
The practical consequence: the 8am–11am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 91.8% on time here.
Cancellations are rare at 0.57%, below the national 1.81% and low enough to earn the plus on the grade. Roughly one flight in 100 is called off; the risk here is arriving late, not not arriving.
Connections and stage length
What a delay here costs
5.8% 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 an hour and a half, 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 is a different operation and performs like one: it runs 89.0% on time across 349 flights, 5 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 5 points of difference.
One caution: this is a thin sample. 350 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 United on IAD to SLC
Put together: treat all of this as provisional. 350 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 83.9% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 347 completed flights over 12 months sit behind that.
Related
Where to go next
- IAD to SLC, every carrier
- United on SLC to IAD, the return leg
- Delta Air Lines on IAD to SLC84.1%
- United Airlines network-wide record
- Washington Dulles International (IAD) delay statistics
- Salt Lake City International (SLC) delay statistics
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
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.