Route reliability record
BOS→SLC
Boston to Salt Lake City
- Flights
- 1,264
- Period
- September 2025 to August 2026
- Distance
- 2,105 mi
- Carriers
- 2
This route sits in the middle of the pack with a C. Close to three flights in four arrive on time by the DOT's definition, 4 points worse than the national rate of 77.3%. The late ones land about an hour behind schedule. That rests on 1,264 BOS to SLC flights, with a median arrival 1 minute early.
Best time to fly BOS to SLC: a 5am–8am departure, ideally on a Monday. Flights in that window arrived on time 87.2% of the time and Monday flights 80.4%, against 73.4% for the route overall.
The US average over the same twelve months is 77.3%, so there is little to separate this route from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
73.4%
Arrivals under 15 minutes late, of 1,240 completed flights
Avg delay
65 min
Across delayed arrivals only, not all flights
Cancelled
1.82%
National rate is 1.89%
Best carrier
Delta
77.5% on time across 1,083 flights
These figures cover 1,264 flights between September 2025 and August 2026. Beyond the headline rate, 8.0% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Carrier by carrier
Which airline is most reliable on BOS to SLC
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 | 77.5% | 67 min | 1.20% | B |
| JetBlue Airwaysthin sample | 181 | 48.0% | 58 min | 5.52% | F− |
Flight by flight
Flights on BOS to SLC
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.
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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 25 points, against half a point between the best and worst carrier.
- 5am–8am365 flights87.2%
- 8am–11am270 flights75.0%
- 11am–2pm112 flights70.5%
- 2pm–5pm32 flights84.4%
- 5pm–8pm485 flights61.9%
- 8pm–5am—
Scale runs 55% to 95%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 61.9% on time, against 87.2% for the 5am–8am slot. By evening the aircraft flying these rotations have absorbed a full day of small delays and there is no slack left to recover in. The 5pm–8pm window is the busiest, with 485 flights scheduled in it.
Explore
Filter BOS to SLC by airline, time, month and day
Pick a breakdown and a carrier. The dashed mark on each row is the same slice for every US flight.
On BOS to SLC, the best departure window is 5am–8am at 87.2% on time and the worst is 5pm–8pm at 61.9%, a wide gap of 25.3 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am87.2%
- 8–11am75.0%
- 11am–2pm70.5%
- 2–5pm84.4%
- 5–8pm61.9%
- 8pm–5am—
best all US flightsScale 55% to 95%. Cells under 30 flights show a dash.
Across the year
When delays peak on this route
This route's year swings by 25 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.
August is the worst month at 62.6% on time, 25 points below September, the best at 88.0%. Summer afternoon convection and peak-season schedules land on the same weeks every year, so this is a pattern you can book around rather than a run of bad luck. March was the busiest month here, with 132 flights.
Across the week, Monday is the strongest day at 80.4% on time and Sunday the weakest at 63.0%, a spread of 17 points.
Delay causes
Why this route gets delayed
Carrier accounts for 45% of the 21,000 delay minutes carriers reported here, and the remaining four split what is left.
- 45%Carrier
- 27%Late-arriving aircraft
- 27%National Airspace System
- 1%Extreme weather
The largest share of delay minutes, 45%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 9,607 of the 21,000 delay minutes reported here. The split is drawn from 21,407 reported delay minutes.
Cancellations sit at 1.82% against a national 1.89%, which is ordinary. Diversions add another 0.08%.
Connections and stage length
What a delay here actually costs
8.0% 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 80.6% on time across 1,264 flights, 7 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 7 points of difference.
The sample behind these figures is 1,264 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 SLC 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. September runs 88.0% on time and August 62.6%, a swing of 25 points. If the dates move at all, move them out of August before you think about anything else. 1,240 completed flights over 12 months sit behind that.
Common questions
BOS to SLC questions
How often is BOS to SLC delayed?
About one flight in four arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 26.6% of the 1,264 flights in this analysis, against 22.7% nationally. Delayed flights are late by about an hour on average.
How reliable is BOS to SLC compared with the rest of the country?
73.4% of flights arrive on time here against a national 77.3%, a difference of 4 points against it. That is worth a C on this site's grading scale.
What time of day has the fewest delays on BOS to SLC?
The 5am–8am departure window is the strongest at 87.2% on time. The 5pm–8pm window is the weakest at 61.9%, 25 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 August delays on BOS to SLC?
August is the weakest month at 62.6% on time, compared with 88.0% in September. Across the year that is 25 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
- SLC to BOS — the return legseparate record
- Boston Logan International (BOS) delay statistics
- Salt Lake City International (SLC) delay statistics
- Delta Air Lines on BOS to SLC77.5%
- JetBlue Airways on BOS to SLC48.0%
- BOS to DCA, a related route72.6%
- DEN to SLC, a related route78.2%
- BOS to ORD, a related route71.9%
- Delta Air Lines on-time record77.5%
- JetBlue Airways on-time record48.0%
- 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
Direction matters. BOS to SLC and SLC to BOS 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, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.