Carrier route record
DLSLC→BOS
Delta Air Lines · Salt Lake City to Boston
- Flights
- 1,083
- Period
- September 2025 to August 2026
- Share of route
- 86%
- Carriers
- 2
Historical statistics for September 2025 to August 2026, not live status. For today’s flights, check with Delta Air Lines.
Delta on SLC to BOS lands a B, 5 points better than the national rate of 77.3%. About one flight in six arrives 15 minutes late or worse, and those flights are late by about an hour on average. That rests on 1,083 flights, with a median arrival 8 minutes early.
Set against the rest of the country, Delta's SLC to BOS record is 5 points better than the US average of 77.3%. That gap is worth roughly 54 fewer late arrivals for every thousand flights.
Key figures
On time
82.7%
Arrivals under 15 minutes late, of 1,067 completed flights
Avg delay
59 min
Across delayed arrivals only, not all flights
Cancelled
1.29%
National rate is 1.89%
Whole route
80.6%
Every carrier on SLC to BOS, 1,264 flights
These figures cover 1,083 flights between September 2025 and August 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.
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Carrier by carrier
Delta against every carrier on SLC to BOS
Delta flew 1,083 of the 1,264 flights on SLC to BOS, most of the route. Its 82.7% on time is 2 points better than the route as a whole, which runs 80.6%. Ranked by on-time rate it is first of two carriers on the route, where the range runs from Delta at 82.7% to JetBlue at 67.6%. 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 Lines (this page) | 1,083 | 82.7% | 59 min | 1.29% | B |
| JetBlue Airwaysthin sample | 181 | 67.6% | 71 min | 6.08% | C− |
Flight by flight
Delta flight numbers on SLC to BOS
Timetable by Aviasales, a Travelpayouts partner. Booking through it may earn this site a commission at no cost to you; it changes no figure here.
Departure window
When Delta runs best on this route
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 15 points, against half a point between the best and worst carrier.
- 5am–8am8 flights—
- 8am–11am374 flights81.1%
- 11am–2pm—
- 2pm–5pm—
- 5pm–8pm363 flights76.2%
- 8pm–5am338 flights91.3%
Scale runs 70% to 95%. Rows with fewer than 30 flights show a dash.
The overnight block holds up unusually well at 91.3% on time across 338 flights. Red-eyes fly into empty airspace and empty gates, and they are the first rotation of the aircraft's day rather than the last. The 8am–11am window is the busiest, with 374 flights scheduled in it.
Across the year
Delta on SLC to BOS through the year
May is the best month on the calendar at 92.4% on time. Shoulder season thins the schedule and takes the summer weather with it, and the operation gets its margin back. March was the busiest month here, with 95 flights.
Across the week, Saturday is the strongest day at 88.2% on time and Sunday the weakest at 78.7%, a spread of 10 points.
Arrival by arrival
How late Delta on SLC to BOS runs when it is late
Delta on SLC to BOS often beats the schedule: 392 of 1,067 completed flights, 37%, arrived 15 minutes or more early. The 185 late arrivals split 71 under half an hour, 53 between 30 and 60 minutes, and 61 an hour or more.
- 15+ min early392 flights36.7%
- Within 15 min490 flights45.9%
- 15–29 min late71 flights6.7%
- 30–59 min late53 flights5.0%
- 1–2 hours late38 flights3.6%
- 2+ hours late23 flights2.2%
Scale runs 0% to 100%.
Share of 1,067 completed flights by arrival against schedule.
41 of 177 late departures made up the time and arrived on time, 23% of them. 49 flights left on time and still arrived late.
The worst days
Worst days for Delta on SLC to BOS
The latest arrival of the period was on 29 December 2025, 5 hours 33 minutes behind schedule; most of its delay minutes were filed as a late-arriving aircraft. The five worst days are spread across December, September, July, January and October, with no single month standing out.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 29 December 2025 | 5 hours 33 minutes | Late-arriving aircraft |
| 24 September 2025 | 4 hours 15 minutes | National Airspace System |
| 13 July 2026 | 4 hours 13 minutes | Late-arriving aircraft |
| 16 January 2026 | 3 hours 58 minutes | Carrier |
| 14 October 2025 | 3 hours 30 minutes | National Airspace System |
Delay causes
Why Delta runs late on this route
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 11,000 reported delay minutes.
- 40%National Airspace System
- 30%Carrier
- 27%Late-arriving aircraft
- 3%Extreme weather
40% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 4,349 minutes out of 11,000, against a national NAS share of 21%. The split is drawn from 10,933 reported delay minutes.
Cancellations sit at 1.29% against a national 1.89%, which is ordinary. Diversions add another 0.18%.
Connections and stage length
What a delay here costs
5.7% of arrivals land an hour or more late, close to the national 8.3%, so a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last about an hour, which a normal layover absorbs.
At 2,105 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 77.5% on time across 1,083 flights, 5 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 5 points of difference.
One caution: this is a thin sample. 1,083 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 SLC to BOS
Put together: treat all of this as provisional. 1,083 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 82.7% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 1,067 completed flights over 12 months sit behind that.
Related
Where to go next
- SLC to BOS, every carrier
- Delta on BOS to SLC, the return leg
- JetBlue Airways on SLC to BOS67.6%
- Delta Air Lines network-wide record
- Salt Lake City International (SLC) delay statistics
- Boston Logan International (BOS) delay statistics
- The best time of day to fly, according to 7.05 million flight records
- Worst months to fly in the US, ranked by the data
Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.