Route reliability record
MCI→SEA
Kansas City to Seattle
- Flights
- 1,131
- Period
- July 2025 to June 2026
- Distance
- 1,490 mi
- Carriers
- 3
This route lands a B, 6 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 a little over an hour on average. That is a workable record, not a spotless one. That rests on 1,131 MCI to SEA flights, with a median arrival 6 minutes early.
Best time to fly MCI to SEA: a 5am–8am departure, ideally on a Tuesday. Flights in that window arrived on time 89.2% of the time and Tuesday flights 88.4%, against 83.4% for the route overall.
Set against the rest of the country, this route's record is 6 points better than the US average of 77.6%. That gap is worth roughly 58 fewer late arrivals for every thousand flights.
Key figures
On time
83.4%
Arrivals under 15 minutes late, of 1,113 completed flights
Avg delay
71 min
Across delayed arrivals only, not all flights
Cancelled
1.06%
National rate is 1.81%
Best carrier
Alaska
83.0% on time across 745 flights
These figures cover 1,131 flights between July 2025 and June 2026. The median arrival is 6 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 MCI to SEA
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 Linesthin sample | 364 | 85.3% | 84 min | 1.65% | A |
| Alaska Airlines | 745 | 83.0% | 67 min | 0.81% | B+ |
| Southwest Airlinesthin sample | 22 | 63.6% | 66 min | 0.00% | D+ |
Flight by flight
Flights on MCI to SEA
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 22 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–8am473 flights89.2%
- 8am–11am173 flights83.4%
- 11am–2pm4 flights—
- 2pm–5pm351 flights82.4%
- 5pm–8pm11 flights—
- 8pm–5am119 flights66.9%
Scale runs 60% to 95%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 89.2% of the time, against 66.9% for the overnight 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. The 5am–8am window is the busiest, with 473 flights scheduled in it.
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.
December is the weak month at 66.3% on time, against 90.9% in February. Winter delays cluster: a single storm system can account for most of a month's shortfall, so an average December hides both very good weeks and genuinely unflyable days. July was the busiest month here, with 127 flights.
Across the week, Tuesday is the strongest day at 88.4% on time and Friday the weakest at 77.4%. 11 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. Carrier accounts for 47% of the 13,000 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.
- 47%Carrier
- 30%Late-arriving aircraft
- 20%National Airspace System
- 3%Extreme weather
The largest share of delay minutes, 47%, 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 6,216 of the 13,000 delay minutes reported here. The split is drawn from 13,183 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 89.2% on time here.
Cancellations sit at 1.06% against a national 1.81%, which is ordinary. Diversions add another 0.53%.
Connections and stage length
What a delay here actually costs
Badly late arrivals are rare here: only 4.9% 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 1,490 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 is a different operation and performs like one: it runs 77.7% on time across 1,131 flights, 6 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 6 points of difference.
The sample behind these figures is 1,131 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 SEA 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. February runs 90.9% on time and December 66.3%, a swing of 25 points. If the dates move at all, move them out of December before you think about anything else. 1,113 completed flights over 12 months sit behind that.
Common questions
MCI to SEA questions
How often is MCI to SEA 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 16.6% of the 1,131 flights in this analysis, against 22.4% nationally. Delayed flights are late by a little over an hour on average.
How reliable is MCI to SEA compared with the rest of the country?
83.4% of flights arrive on time here against a national 77.6%, a difference of 6 points in its favour. That is worth a B on this site's grading scale.
What time of day has the fewest delays on MCI to SEA?
The 5am–8am departure window is the strongest at 89.2% on time. The 8pm–5am window is the weakest at 66.9%, 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 December delays on MCI to SEA?
December is the weakest month at 66.3% on time, compared with 90.9% in February. 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
- SEA to MCI — the return legseparate record
- Kansas City International (MCI) delay statistics
- Seattle-Tacoma International (SEA) delay statistics
- Delta Air Lines on MCI to SEA85.3%
- Alaska Airlines on MCI to SEA83.0%
- MCI to DEN, a related route76.1%
- LAX to SEA, a related route85.4%
- MCI to ORD, a related route74.7%
- Delta Air Lines on-time record85.3%
- Alaska Airlines on-time record83.0%
- Southwest Airlines on-time record63.6%
- The best time of day to fly, according to 7.04 million flight records
- Worst months to fly in the US, ranked by the data
Direction matters. MCI to SEA and SEA to MCI 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.