Carrier route record
DLBOI→SLC
Delta Air Lines · Boise to Salt Lake City
- Flights
- 1,223
- Period
- July 2025 to June 2026
- Share of route
- 70%
- Carriers
- 2
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Delta Air Lines.
Delta on BOI to SLC earns an A. Close to nine flights in ten arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 13 points better than the national rate of 77.6%. When something does go wrong the average delay runs an hour and a half. That rests on 1,223 flights, with a median arrival 11 minutes early.
Set against the rest of the country, Delta's BOI to SLC record is 13 points better than the US average of 77.6%. That gap is worth roughly 129 fewer late arrivals for every thousand flights.
Key figures
On time
90.5%
Arrivals under 15 minutes late, of 1,205 completed flights
Avg delay
93 min
Across delayed arrivals only, not all flights
Cancelled
1.31%
National rate is 1.81%
Whole route
92.0%
Every carrier on BOI to SLC, 1,740 flights
These figures cover 1,223 flights between July 2025 and June 2026. The median arrival is 11 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 BOI to SLC
Delta flew 1,223 of the 1,740 flights on BOI to SLC, most of the route. Its 90.5% on time is 2 points worse than the route as a whole, which runs 92.0%. Ranked by on-time rate it is last of two carriers on the route, where the range runs from SkyWest at 95.3% to Delta at 90.5%.
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 |
|---|---|---|---|---|---|
| SkyWest Airlines | 517 | 95.3% | 47 min | 0.19% | A+ |
| Delta Air Lines (this page) | 1,223 | 90.5% | 93 min | 1.31% | A |
Flight by flight
Delta flight numbers on BOI to SLC
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 1,223 flights.
- 5am–8am359 flights90.9%
- 8am–11am182 flights92.3%
- 11am–2pm522 flights90.1%
- 2pm–5pm—
- 5pm–8pm160 flights89.2%
- 8pm–5am—
Scale runs 80% to 100%. Rows with fewer than 30 flights show a dash.
The time of day barely matters here. The 8am–11am window tops the set at 92.3% and 5pm–8pm sits at 89.2%, 3 points apart across 1,223 flights. Pick the departure that suits the trip: whatever is going wrong here is not accumulating over the course of the day. The 11am–2pm window is the busiest, with 522 flights scheduled in it.
Across the year
Delta on BOI to SLC through the year
January is the weak month at 83.5% on time, against 95.9% in July. 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. July was the busiest month here, with 123 flights.
Across the week, Friday is the strongest day at 92.5% on time and Thursday the weakest at 88.5%. 4 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 56% of the 11,000 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.
- 56%Carrier
- 31%Late-arriving aircraft
- 10%National Airspace System
- 3%Extreme weather
The largest share of delay minutes, 56%, 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 5,942 of the 11,000 delay minutes reported here. The split is drawn from 10,540 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 92.3% on time here.
Cancellations sit at 1.31% against a national 1.81%, which is ordinary. Diversions add another 0.16%.
Connections and stage length
What a delay here costs
Badly late arrivals are rare here: only 3.4% land an hour or more behind schedule, against 8.1% nationally. Connections built on this flight are about as safe as US domestic connections get, though a cancelled flight still ignores every layover you give it.
At 290 miles this is a short hop, and stage length matters more than it looks. A flight this short spends under two hours in the air, which leaves almost nothing to claw back a late pushback with. Delay here is decided on the ground, in the turn, which is why the 8am–11am window matters as much as it does.
The return leg is a different operation and performs like one: it runs 84.7% on time across 1,223 flights, 6 points below 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 6 points of difference.
The sample behind these figures is 1,223 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 Delta on BOI to SLC
Put together: the calendar is the biggest lever here, not the carrier or the hour. July runs 95.9% on time and January 83.5%, a swing of 12 points. If the dates move at all, move them out of January before you think about anything else. 1,205 completed flights over 12 months sit behind that.
Related
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.