Route reliability record
SEA→BOI
Seattle to Boise
- Flights
- 3,829
- Period
- September 2025 to August 2026
- Distance
- 399 mi
- Carriers
- 2
This route earns an A+. More than four flights in five arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 9 points better than the national rate of 77.3%. When something does go wrong the average delay runs roughly 50 minutes. That rests on 3,829 SEA to BOI flights, of which SkyWest Airlines flew 2,853 at 87.8% on time.
Best time to fly SEA to BOI: a 5am–8am departure, ideally on a Saturday. Flights in that window arrived on time 92.0% of the time and Saturday flights 91.2%, against 86.3% for the route overall.
Set against the rest of the country, this route's record is 9 points better than the US average of 77.3%. That gap is worth roughly 90 fewer late arrivals for every thousand flights.
Key figures
On time
86.3%
Arrivals under 15 minutes late, of 3,815 completed flights
Avg delay
51 min
Across delayed arrivals only, not all flights
Cancelled
0.26%
National rate is 1.89%
Best carrier
SkyWest
87.8% on time across 2,853 flights
These figures cover 3,829 flights between September 2025 and August 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.
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Carrier by carrier
Which airline is most reliable on SEA to BOI
The two carriers here are closely matched: 6 points separate the best from the worst. At that spread, schedule and price are better tie-breakers than reliability. Sample sizes are shown so you can see which rows are worth weighing.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| SkyWest Airlines | 2,853 | 87.8% | 55 min | 0.21% | A+ |
| Alaska Airlines | 976 | 82.2% | 45 min | 0.41% | B+ |
No carrier stands out. SkyWest tops the table at 87.8%, 6 points clear of the bottom, which is inside the range this kind of sample moves year to year.
Flight by flight
Flights on SEA to BOI
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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Best ways to make this trip
The most reliable ways to fly Seattle to Boise
Every airline on this route, ranked by how often a scheduled flight actually operated and arrived on time, with its best departure time and most punctual flight number. No nearby airport pair beat these.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. SEA → BOISeattle to Boise | SkyWest Airlines | 87.6% | 87.8% | 0.21% | 5am–8am, Sat | OO 3750 07:15 |
| 2. SEA → BOISeattle to Boise | Alaska Airlines | 81.9% | 82.2% | 0.41% | 8am–11am, Wed | — |
Success is the share of scheduled flights that operated and arrived less than 15 minutes late, so a cancelled flight counts against it. “(route)” means the best time comes from every carrier on the route rather than this airline alone.
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 13 points, against 6 points between the best and worst carrier.
- 5am–8am490 flights92.0%
- 8am–11am650 flights89.5%
- 11am–2pm757 flights88.5%
- 2pm–5pm516 flights85.2%
- 5pm–8pm643 flights85.4%
- 8pm–5am773 flights79.5%
Scale runs 70% to 95%.
Book the early departure. Flights leaving between 5am–8am arrive on time 92.0% of the time, against 79.5% for the overnight window. That is 13 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 8pm–5am window is the busiest, with 773 flights scheduled in it.
Explore
Filter SEA to BOI 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 SEA to BOI, the best departure window is 5am–8am at 92.0% on time and the worst is 8pm–5am at 79.5%, a wide gap of 12.5 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am92.0%
- 8–11am89.5%
- 11am–2pm88.5%
- 2–5pm85.2%
- 5–8pm85.4%
- 8pm–5am79.5%
best all US flightsScale 60% to 95%.
Across the year
When delays peak on this route
This route's year swings by 13 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.
July is the worst month at 78.8% on time, 13 points below October, the best at 91.6%. 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 369 flights.
Across the week, Saturday is the strongest day at 91.2% on time and Thursday the weakest at 83.1%, a spread of 8 points.
Delay causes
Why this route gets delayed
Carrier accounts for 54% of the 27,000 delay minutes carriers reported here, and the remaining four split what is left.
- 54%Carrier
- 18%Late-arriving aircraft
- 17%Extreme weather
- 11%National Airspace System
- 0%Security
Extreme weather accounts for 17% of delay minutes, well above the single-digit share typical across the system. Weather delays are lumpy: they arrive as whole bad days rather than as a steady drag, so the monthly strip above is the more useful view of the risk. The national share is 6%, so this operation carries roughly 2.8 times the usual weather exposure. The split is drawn from 26,802 reported delay minutes.
The largest share of delay minutes, 54%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 14,000 of the 27,000 delay minutes reported here.
Cancellations are rare at 0.26%, below the national 1.89% and low enough to earn the plus on the grade. Roughly one flight in 100 is called off; the risk here is arriving late, not not arriving.
Connections and stage length
What a delay here actually costs
Badly late arrivals are rare here: only 3.7% land an hour or more behind schedule, against 8.3% 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 399 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 5am–8am window matters as much as it does.
The return leg runs 84.9% on time across 3,730 flights, within about a point of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.
The sample behind these figures is 3,829 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 BOI 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. October runs 91.6% on time and July 78.8%, a swing of 13 points. If the dates move at all, move them out of July before you think about anything else. 3,815 completed flights over 12 months sit behind that.
Common questions
SEA to BOI questions
How often is SEA to BOI delayed?
About one flight in seven arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 13.7% of the 3,829 flights in this analysis, against 22.7% nationally. Delayed flights are late by roughly 50 minutes on average.
Which airline is most reliable on SEA to BOI?
SkyWest Airlines leads at 87.8% on time across 2,853 flights. Alaska Airlines is at the other end on 82.2%, a gap of 6 points. Sample size matters as much as the percentage: a rate built from a few hundred flights moves around far more than one built from ten thousand.
What time of day has the fewest delays on SEA to BOI?
The 5am–8am departure window is the strongest at 92.0% on time. The 8pm–5am window is the weakest at 79.5%, 13 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 July delays on SEA to BOI?
July is the weakest month at 78.8% on time, compared with 91.6% in October. Across the year that is 13 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
- BOI to SEA — the return legseparate record
- Seattle-Tacoma International (SEA) delay statistics
- SkyWest Airlines on SEA to BOI87.8%
- Alaska Airlines on SEA to BOI82.2%
- SEA to LAX, a related route82.0%
- DEN to BOI, a related route76.3%
- SEA to PHX, a related route78.2%
- SkyWest Airlines on-time record87.8%
- Alaska Airlines on-time record82.2%
- 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. SEA to BOI and BOI to SEA 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.