Route reliability record
SEA→MCI
Seattle to Kansas City
- Flights
- 1,126
- Period
- September 2025 to August 2026
- Distance
- 1,490 mi
- Carriers
- 3
This route lands a B+, 4 points better than the national rate of 77.3%. About one flight in five arrives 15 minutes late or worse, and those flights are late by about an hour on average. That rests on 1,126 SEA to MCI flights, with a median arrival 8 minutes early.
Best time to fly SEA to MCI: a 5am–8am departure, ideally on a Tuesday. Flights in that window arrived on time 94.3% of the time and Tuesday flights 85.1%, against 81.2% 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
81.2%
Arrivals under 15 minutes late, of 1,109 completed flights
Avg delay
59 min
Across delayed arrivals only, not all flights
Cancelled
0.80%
National rate is 1.89%
Best carrier
Alaska
84.3% on time across 745 flights
These figures cover 1,126 flights between September 2025 and August 2026. The median arrival is 8 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 MCI
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 |
|---|---|---|---|---|---|
| Alaska Airlines | 745 | 84.3% | 45 min | 0.40% | B+ |
| Delta Air Linesthin sample | 364 | 77.4% | 77 min | 1.65% | B |
| Southwest Airlinesthin sample | 17 | 29.4% | 76 min | 0.00% | F+ |
Flight by flight
Flights on SEA to MCI
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 32 points, against half a point between the best and worst carrier.
- 5am–8am70 flights94.3%
- 8am–11am271 flights88.8%
- 11am–2pm129 flights77.5%
- 2pm–5pm32 flights62.5%
- 5pm–8pm623 flights78.1%
- 8pm–5am1 flights—
Scale runs 55% to 100%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 94.3% of the time, against 62.5% for the afternoon window. That is 32 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 623 flights scheduled in it.
Explore
Filter SEA to MCI 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 MCI, the best departure window is 5am–8am at 94.3% on time and the worst is 2pm–5pm at 62.5%, a wide gap of 31.8 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am94.3%
- 8–11am88.8%
- 11am–2pm77.5%
- 2–5pm62.5%
- 5–8pm78.1%
- 8pm–5am—
best all US flightsScale 55% to 100%. Cells under 30 flights show a dash.
Across the year
When delays peak on this route
This route's year swings by 22 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.
April is the best month on the calendar at 94.3% on time. Shoulder season thins the schedule and takes the summer weather with it, and the operation gets its margin back. July was the busiest month here, with 127 flights.
Across the week, Tuesday is the strongest day at 85.1% on time and Monday the weakest at 78.6%, a spread of 7 points.
Delay causes
Why this route gets delayed
Carrier accounts for 54% of the 12,000 delay minutes carriers reported here, and the remaining four split what is left.
- 54%Carrier
- 32%Late-arriving aircraft
- 12%National Airspace System
- 2%Extreme weather
The largest share of delay minutes, 54%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 6,624 of the 12,000 delay minutes reported here. The split is drawn from 12,263 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 94.3% on time here.
Cancellations are rare at 0.80%, 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
5.6% 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.
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.
The return leg is a different operation and performs like one: it runs 85.0% on time across 1,126 flights, 4 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 4 points of difference.
The sample behind these figures is 1,126 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 MCI 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. April runs 94.3% on time and September 72.5%, a swing of 22 points. If the dates move at all, move them out of September before you think about anything else. 1,109 completed flights over 12 months sit behind that.
Common questions
SEA to MCI questions
How often is SEA to MCI delayed?
About one flight in five arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 18.8% of the 1,126 flights in this analysis, against 22.7% nationally. Delayed flights are late by about an hour on average.
How reliable is SEA to MCI compared with the rest of the country?
81.2% of flights arrive on time here against a national 77.3%, a difference of 4 points in its favour. That is worth a B+ on this site's grading scale.
What time of day has the fewest delays on SEA to MCI?
The 5am–8am departure window is the strongest at 94.3% on time. The 2pm–5pm window is the weakest at 62.5%, 32 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 September delays on SEA to MCI?
September is the weakest month at 72.5% on time, compared with 94.3% in April. Across the year that is 22 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
- MCI to SEA — the return legseparate record
- Seattle-Tacoma International (SEA) delay statistics
- Kansas City International (MCI) delay statistics
- Alaska Airlines on SEA to MCI84.3%
- Delta Air Lines on SEA to MCI77.4%
- SEA to LAX, a related route82.0%
- DEN to MCI, a related route76.5%
- SEA to PHX, a related route78.2%
- Alaska Airlines on-time record84.3%
- Delta Air Lines on-time record77.4%
- Southwest Airlines on-time record29.4%
- 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 MCI and MCI 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.