Route reliability record

SJC→SEA

San Jose to Seattle

Flights: 4,368
Period: July 2025 to June 2026
Distance: 696 mi
Carriers: 5

This route lands a B+, 6 points better than the national rate of 77.6%. About one flight in six arrive 15 minutes late or worse, and those flights are late by roughly 50 minutes on average. That is a workable record, not a spotless one. That rests on 4,368 flights, of which SkyWest Airlines flew 1,563 at 89.5% on time.

SkyWest Airlines is the most reliable of the three carriers covered here at 89.5% on time across 1,563 flights.

On time

83.3%

Arrivals under 15 minutes late, of 4,332 completed flights

Avg delay

52 min

Across delayed arrivals only, not all flights

Cancelled

0.78%

National rate is 1.81%

Best carrier

SkyWest

89.5% on time across 1,563 flights

These figures cover 4,368 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 SJC to SEA

The choice of carrier is not cosmetic here. SkyWest Airlines arrives on time 89.5% of the time; Southwest Airlines manages 75.6%. Sample sizes sit next to every figure, because a two-point gap across 928 flights means less than a ten-point one.

On-time performance by carrier on SJC to SEA
Airline	Flights	On time	Avg delay	Cancelled	Grade
United Airlinesthin sample	1	100.0%	—	0.00%	A+
American Airlinesthin sample	2	100.0%	—	0.00%	A+
SkyWest Airlines	1,563	89.5%	66 min	0.19%	A+
Alaska Airlines	1,874	82.0%	49 min	1.65%	B
Southwest Airlines	928	75.6%	45 min	0.00%	B+

The spread between SkyWest and Southwest is 14 points, wide enough that it should decide the booking. On a hundred trips that is 14 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 28 points, against 14 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am782 flights95.4%
8am–11am632 flights79.5%
11am–2pm773 flights86.8%
2pm–5pm924 flights83.2%
5pm–8pm977 flights78.0%
8pm–5am280 flights67.5%

Scale runs 60% to 100%. Rows with fewer than 30 flights show a dash.

Book the early departure. Flights leaving between 5am–8am arrive on time 95.4% of the time, against 67.5% for the overnight window. That is 28 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 5pm–8pm window is the busiest, with 977 flights scheduled in it.

Across the year

When delays peak on this route

This route's year swings by 16 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.

Darker means more delays. Figures are on-time percentages.February best, June worst

June is the worst month at 76.8% on time, 16 points below February, the best at 92.9%. 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. July was the busiest month here, with 425 flights.

Across the week, Wednesday is the strongest day at 89.0% on time and Sunday the weakest at 79.5%. 10 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 37,000 reported delay minutes.

Carrier
35%
Late-arriving aircraft
33%
National Airspace System
24%
Extreme weather
7%
Security
0%

The largest share of delay minutes, 35%, 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 13,000 of the 37,000 delay minutes reported here. The split is drawn from 37,287 reported delay minutes.

The practical consequence: the 5am–8am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 95.4% on time here.

Cancellations are rare at 0.78%, below the national 1.81% 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 3.8% land an hour or more behind schedule, against 8.1% 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 696 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 81.6% on time across 4,371 flights, within 2 points 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 4,368 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. February runs 92.9% on time and June 76.8%, a swing of 16 points. If the dates move at all, move them out of June before you think about anything else. 4,332 completed flights over 12 months sit behind that.

Common questions

SJC to SEA questions

How often is SJC to SEA delayed?

About one flight in six arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 16.7% of the 4,368 flights in this analysis, against 22.4% nationally. Delayed flights are late by roughly 50 minutes on average.

Which airline is most reliable on SJC to SEA?

SkyWest Airlines leads at 89.5% on time across 1,563 flights. Southwest Airlines is at the other end on 75.6%, a gap of 14 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 SJC to SEA?

The 5am–8am departure window is the strongest at 95.4% on time. The 8pm–5am window is the weakest at 67.5%, 28 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 SJC to SEA?

June is the weakest month at 76.8% on time, compared with 92.9% in February. Across the year that is 16 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.

Where to go next

Direction matters. SJC to SEA and SEA to SJC 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, July 2025 to June 2026. Updated monthly. How this data is collected.

Key figures