Route reliability record
SLC→BOS
Salt Lake City to Boston
- Flights
- 1,256
- Period
- July 2025 to June 2026
- Distance
- 2,105 mi
- Carriers
- 2
This route lands a B, 5 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 about an hour on average. That is a workable record, not a spotless one. That rests on 1,256 SLC to BOS flights, with a median arrival 9 minutes early.
Best time to fly SLC to BOS: a 8pm–5am departure, ideally on a Saturday. Flights in that window arrived on time 87.3% of the time and Saturday flights 88.4%, against 82.2% for the route overall.
Set against the rest of the country, this route's record is 5 points better than the US average of 77.6%. That gap is worth roughly 46 fewer late arrivals for every thousand flights.
Key figures
On time
82.2%
Arrivals under 15 minutes late, of 1,233 completed flights
Avg delay
61 min
Across delayed arrivals only, not all flights
Cancelled
1.75%
National rate is 1.81%
Best carrier
Delta
83.3% on time across 1,083 flights
These figures cover 1,256 flights between July 2025 and June 2026. The median arrival is 9 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
Which airline is most reliable on SLC to BOS
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 | 1,083 | 83.3% | 60 min | 1.29% | B |
| JetBlue Airwaysthin sample | 173 | 74.5% | 67 min | 4.62% | C− |
Flight by flight
Flights on SLC to BOS
The flight numbers below flew this route at least 250 times in the period, busiest first. Each has its own record, with its schedule and delay causes.
Departure window
The best time of day to leave
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 10 points, against half a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am8 flights—
- 8am–11am374 flights81.6%
- 11am–2pm26 flights—
- 2pm–5pm—
- 5pm–8pm364 flights77.2%
- 8pm–5am484 flights87.3%
Scale runs 70% to 95%. Rows with fewer than 30 flights show a dash.
The overnight block holds up unusually well at 87.3% on time across 484 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 8pm–5am window is the busiest, with 484 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 17 points from best month to worst, which is wide. An annual average tells you very little about the week you are actually flying, so read the strip rather than the headline if your dates are fixed.
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 132 flights.
Across the week, Saturday is the strongest day at 88.4% on time and Thursday the weakest at 76.8%. 12 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
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 14,000 reported delay minutes.
- 36%Late-arriving aircraft
- 33%Carrier
- 30%National Airspace System
- 1%Extreme weather
36% 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 14,000 reported delay minutes here, that single category outweighs weather by 29 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 13,518 reported delay minutes.
Cancellations sit at 1.75% against a national 1.81%, which is ordinary. Diversions add another 0.08%.
Connections and stage length
What a delay here actually costs
6.3% 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 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 75.4% on time across 1,256 flights, 7 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 7 points of difference.
The sample behind these figures is 1,256 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.
Work out the risk of missing a connection in BOS after this flight
What to do with this
Booking this route
Put together: the calendar is the biggest lever here, not the carrier or the hour. May runs 92.4% on time and October 75.0%, a swing of 17 points. If the dates move at all, move them out of October before you think about anything else. 1,233 completed flights over 12 months sit behind that.
Common questions
SLC to BOS questions
How often is SLC to BOS delayed?
About one flight in six arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 17.8% of the 1,256 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.
How reliable is SLC to BOS compared with the rest of the country?
82.2% of flights arrive on time here against a national 77.6%, a difference of 5 points in its favour. That is worth a B on this site's grading scale.
What time of day has the fewest delays on SLC to BOS?
The 8pm–5am departure window is the strongest at 87.3% on time. The 5pm–8pm window is the weakest at 77.2%, 10 points behind. Later departures inherit delays from earlier flights the same aircraft has already flown, which is why the curve slopes the way it does.
How bad are October delays on SLC to BOS?
October is the weakest month at 75.0% on time, compared with 92.4% in May. Across the year that is 17 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.
Related
Where to go next
- BOS to SLC — the return legseparate record
- Salt Lake City International (SLC) delay statistics
- Boston Logan International (BOS) delay statistics
- Delta Air Lines on SLC to BOS83.3%
- JetBlue Airways on SLC to BOS74.5%
- SLC to DEN, a related route77.8%
- DCA to BOS, a related route71.4%
- SLC to PHX, a related route83.9%
- Delta Air Lines on-time record83.3%
- JetBlue Airways on-time record74.5%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
Direction matters. SLC to BOS and BOS to SLC are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
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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.