Route reliability record
SEA→SMF
Seattle to Sacramento
- Flights
- 4,429
- Period
- June 2025 to May 2026
- Distance
- 605 mi
- Carriers
- 3
This route lands a B+, 4 points better than the national rate of 77.4%. About one flight in five arrive 15 minutes late or worse, and those flights are late by about 50 minutes on average. That is a workable record, not a spotless one. That rests on 4,429 flights, of which SkyWest Airlines flew 1,979 at 88.6% on time.
SkyWest Airlines is the most reliable of the three carriers covered here at 88.6% on time across 1,979 flights.
Key figures
On time
80.9%
Arrivals under 15 minutes late, of 4,401 completed flights
Avg delay
51 min
Across delayed arrivals only, not all flights
Cancelled
0.41%
National rate is 1.80%
Best carrier
SkyWest
88.6% on time across 1,979 flights
These figures cover 4,429 flights between June 2025 and May 2026. The median arrival is 5 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 SEA to SMF
The choice of carrier is not cosmetic here. SkyWest Airlines arrives on time 88.6% of the time; Southwest Airlines manages 71.0%. Sample sizes sit next to every figure, because a two-point gap across 1,170 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| SkyWest Airlines | 1,979 | 88.6% | 61 min | 0.25% | A+ |
| Alaska Airlines | 1,280 | 78.0% | 45 min | 0.62% | B+ |
| Southwest Airlines | 1,170 | 71.0% | 49 min | 0.43% | C+ |
The spread between SkyWest and Southwest is 18 points, wide enough that it should decide the booking. On a hundred trips that is 18 more arrivals inside the on-time window.
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 22 points, against 18 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am427 flights92.9%
- 8am–11am1,118 flights90.5%
- 11am–2pm611 flights74.2%
- 2pm–5pm818 flights78.5%
- 5pm–8pm494 flights71.3%
- 8pm–5am961 flights75.7%
Scale runs 65% to 100%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 92.9% of the time, against 71.3% for the evening window. That is 22 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on.
Across the year
When delays peak on this route
This route's year swings by 14 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.
June is the worst month at 73.3% on time, 14 points below April, the best at 87.5%. 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.
Across the week, Tuesday is the strongest day at 84.7% on time and Thursday the weakest at 77.8%. 7 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
One category carries most of the weight here. Late-arriving aircraft accounts for 46% of the 43,000 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.
- 46%Late-arriving aircraft
- 39%Carrier
- 8%National Airspace System
- 7%Extreme weather
- 1%Security
46% 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 43,000 reported delay minutes here, that single category outweighs weather by 7 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 largest share of delay minutes, 39%, 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 17,000 of the 43,000 delay minutes reported here.
Cancellations are rare at 0.41%, below the national 1.80% 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 4.8% land an hour or more behind schedule, against 8.2% 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.
The 605 miles between these two airports put this in the middle of the US network, around two and a half to three hours of block time. That is enough cruise to absorb a ten-minute late pushback and not enough to absorb thirty. It is also long enough that the aircraft usually flies three or four legs a day rather than six, which slows how fast delay compounds.
The return leg runs 82.1% on time across 4,439 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 4,429 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 this route
Put together: the calendar is the biggest lever here, not the carrier or the hour. April runs 87.5% on time and June 73.3%, a swing of 14 points. If the dates move at all, move them out of June before you think about anything else.
Common questions
SEA to SMF questions
How often is SEA to SMF delayed?
About one flight in five arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 19.1% of the 4,429 flights in this analysis, against 22.6% nationally. Delayed flights are late by about 50 minutes on average.
Which airline is most reliable on SEA to SMF?
SkyWest Airlines leads at 88.6% on time across 1,979 flights. Southwest Airlines is at the other end on 71.0%, a gap of 18 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 SMF?
The 5am–8am departure window is the strongest at 92.9% on time. The 5pm–8pm window is the weakest at 71.3%, 22 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 June delays on SEA to SMF?
June is the weakest month at 73.3% on time, compared with 87.5% in April. Across the year that is 14 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
- SMF to SEA — the return legseparate record
- Seattle-Tacoma International (SEA) delay statistics
- Sacramento International (SMF) delay statistics
- SkyWest Airlines on-time record88.6%
- Alaska Airlines on-time record78.0%
- Southwest Airlines on-time record71.0%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.05 million flight records
Direction matters. SEA to SMF and SMF to SEA are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
Source: US DOT Bureau of Transportation Statistics, on-time performance data, June 2025 to May 2026. Updated monthly. How this data is collected.