Carrier route record
DLSLC→BOI
Delta Air Lines · Salt Lake City to Boise
- 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 SLC to BOI 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 about an hour. That rests on 1,223 flights, with a median arrival 8 minutes early.
Set against the rest of the country, Delta's SLC to BOI record is 7 points better than the US average of 77.6%. That gap is worth roughly 71 fewer late arrivals for every thousand flights.
Key figures
On time
84.7%
Arrivals under 15 minutes late, of 1,210 completed flights
Avg delay
59 min
Across delayed arrivals only, not all flights
Cancelled
1.06%
National rate is 1.81%
Whole route
87.1%
Every carrier on SLC to BOI, 1,742 flights
These figures cover 1,223 flights between July 2025 and June 2026. The median arrival is 8 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 SLC to BOI
Delta flew 1,223 of the 1,742 flights on SLC to BOI, most of the route. Its 84.7% on time is 2 points worse than the route as a whole, which runs 87.1%. Ranked by on-time rate it is last of two carriers on the route, where the range runs from SkyWest at 92.6% to Delta at 84.7%.
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 | 519 | 92.6% | 50 min | 0.19% | A+ |
| Delta Air Lines (this page) | 1,223 | 84.7% | 59 min | 1.06% | B |
Flight by flight
Delta flight numbers on SLC to BOI
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–8am—
- 8am–11am570 flights85.9%
- 11am–2pm73 flights87.7%
- 2pm–5pm160 flights86.9%
- 5pm–8pm17 flights—
- 8pm–5am403 flights81.7%
Scale runs 75% to 95%. Rows with fewer than 30 flights show a dash.
The best window here is not the first bank but the 11am–2pm slot at 87.7% on time, ahead of 8pm–5am at 81.7%. Where the curve peaks mid-day rather than at dawn, the constraint is usually congestion at one end rather than the aircraft's own rotation. The 8am–11am window is the busiest, with 570 flights scheduled in it.
Across the year
Delta on SLC to BOI through the year
December is the weak month at 76.2% on time, against 89.3% in June. 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, Tuesday is the strongest day at 90.1% on time and Monday the weakest at 81.8%. 8 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 64% 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.
- 64%Carrier
- 22%Late-arriving aircraft
- 8%National Airspace System
- 6%Extreme weather
The largest share of delay minutes, 64%, 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 6,990 of the 11,000 delay minutes reported here. The split is drawn from 10,909 reported delay minutes.
Cancellations sit at 1.06% against a national 1.81%, which is ordinary. Diversions add another 0.00%.
Connections and stage length
What a delay here costs
Badly late arrivals are rare here: only 4.5% 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 11am–2pm window matters as much as it does.
The return leg is a different operation and performs like one: it runs 90.5% on time across 1,223 flights, 6 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 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 SLC to BOI
Put together: the calendar is the biggest lever here, not the carrier or the hour. June runs 89.3% on time and December 76.2%, a swing of 13 points. If the dates move at all, move them out of December before you think about anything else. 1,210 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.