Route reliability record
SEA→MCI
Seattle to Kansas City
- Flights
- 1,131
- Period
- July 2025 to June 2026
- Distance
- 1,490 mi
- Carriers
- 3
This route lands a B+, level with the national rate of 77.6%. Roughly one flight in four arrives 15 minutes late or worse, and those flights are late by about an hour on average. That is a workable record, not a spotless one. That rests on 1,131 SEA to MCI flights, with a median arrival 5 minutes early.
Best time to fly SEA to MCI: a 8am–11am departure, ideally on a Wednesday. Flights in that window arrived on time 86.4% of the time and Wednesday flights 82.8%, against 77.7% for the route overall.
The US average over the same twelve months is 77.6%, 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
77.7%
Arrivals under 15 minutes late, of 1,114 completed flights
Avg delay
55 min
Across delayed arrivals only, not all flights
Cancelled
0.88%
National rate is 1.81%
Best carrier
Alaska
79.3% on time across 745 flights
These figures cover 1,131 flights between July 2025 and June 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 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 | 79.3% | 48 min | 0.54% | B+ |
| Delta Air Linesthin sample | 364 | 76.6% | 68 min | 1.65% | B |
| Southwest Airlinesthin sample | 22 | 45.5% | 55 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.
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 15 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–8am21 flights—
- 8am–11am318 flights86.4%
- 11am–2pm145 flights71.0%
- 2pm–5pm28 flights—
- 5pm–8pm618 flights74.0%
- 8pm–5am1 flights—
Scale runs 65% to 90%. Rows with fewer than 30 flights show a dash.
The weak window here is the middle of the day, not the evening: 11am–2pm runs 71.0% on time against 86.4% for 8am–11am. That shape usually means a departure bank rather than an accumulating delay, so the recovery later in the afternoon is real rather than noise. The 5pm–8pm window is the busiest, with 618 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 38 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 56.3% on time, 38 points below April, the best at 94.3%. 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 127 flights.
Across the week, Wednesday is the strongest day at 82.8% on time and Friday the weakest at 74.3%. 9 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 50% of the 14,000 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.
- 50%Carrier
- 31%Late-arriving aircraft
- 16%National Airspace System
- 3%Extreme weather
The largest share of delay minutes, 50%, 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 6,833 of the 14,000 delay minutes reported here. The split is drawn from 13,686 reported delay minutes.
The practical consequence: the 8am–11am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 86.4% on time here.
Cancellations are rare at 0.88%, 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
6.4% of arrivals land an hour or more late, close to the national 8.1%. That is the figure that decides a connection, and it says 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. 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 83.4% on time across 1,131 flights, 6 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 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 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 July 56.3%, a swing of 38 points. If the dates move at all, move them out of July before you think about anything else. 1,114 completed flights over 12 months sit behind that.
Common questions
SEA to MCI questions
How often is SEA to MCI delayed?
Roughly one flight in four arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 22.3% of the 1,131 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.
How reliable is SEA to MCI compared with the rest of the country?
77.7% of flights arrive on time here against a national 77.6%, a difference of half a point 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 8am–11am departure window is the strongest at 86.4% on time. The 11am–2pm window is the weakest at 71.0%, 15 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 MCI?
July is the weakest month at 56.3% on time, compared with 94.3% in April. Across the year that is 38 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 MCI79.3%
- Delta Air Lines on SEA to MCI76.6%
- SEA to LAX, a related route83.4%
- DEN to MCI, a related route75.5%
- SEA to PHX, a related route79.2%
- Alaska Airlines on-time record79.3%
- Delta Air Lines on-time record76.6%
- Southwest Airlines on-time record45.5%
- 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. 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.
Embed SEA to MCI’s on-time badge on your site
Paste this into a web page. The badge shows the current on-time rate, cancellation rate and grade, and updates every month. Preview it, or build a badge for another route or airport.
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.