Carrier route record

DLMCI→SEA

Delta Air Lines · Kansas City to Seattle

Flights: 364
Period: July 2025 to June 2026
Share of route: 32%
Carriers: 3

Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Delta Air Lines.

Delta on MCI to SEA earns an A. More than four flights in five arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 8 points better than the national rate of 77.6%. When something does go wrong the average delay runs an hour and a half. That rests on 364 flights, with a median arrival 10 minutes early.

Set against the rest of the country, Delta's MCI to SEA record is 8 points better than the US average of 77.6%. That gap is worth roughly 77 fewer late arrivals for every thousand flights.

On time

85.3%

Arrivals under 15 minutes late, of 354 completed flights

Avg delay

84 min

Across delayed arrivals only, not all flights

Cancelled

1.65%

National rate is 1.81%

Whole route

83.4%

Every carrier on MCI to SEA, 1,131 flights

These figures cover 364 flights between July 2025 and June 2026. The median arrival is 10 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

Delta against every carrier on MCI to SEA

Delta flew 364 of the 1,131 flights on MCI to SEA, about 32% of it. Its 85.3% on time is 2 points better than the route as a whole, which runs 83.4%. Ranked by on-time rate it is first of three carriers on the route, where the range runs from Delta at 85.3% to Southwest at 63.6%. One of those carriers flew fewer than 365 flights here, so treat their positions as rough.

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.

On-time performance by carrier on MCI to SEA
Airline	Flights	On time	Avg delay	Cancelled	Grade
Delta Air Lines (this page)thin 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

Delta flight numbers on MCI to SEA

DL 210507:5585.3% · 364 flights

Departure window

When Delta runs best on this route

Departure time is the single lever a traveller controls, and it moves the odds more than most people expect. Each bar below is the on-time rate for flights scheduled to leave inside that window, across 364 flights.

5am–8am191 flights87.0%
8am–11am173 flights83.4%
11am–2pm—
2pm–5pm—
5pm–8pm—
8pm–5am—

Scale runs 75% to 90%. Rows with fewer than 30 flights show a dash.

The 5am–8am window is the strongest at 87.0% on time. The full set of windows spans 4 points.

Across the year

Delta on MCI to SEA through the year

Jul–Sep 202592 flights89.0%
Oct–Dec 202591 flights82.0%
Jan–Mar 202690 flights81.4%
Apr–Jun 202691 flights88.6%

Scale runs 75% to 95%. Rows with fewer than 30 flights show a dash.

Monthly volumes are too low here to break the year into twelve reliable readings. What the twelve-month total says is 85.3% on time across 364 flights.

Quarter by quarter Delta on MCI to SEA held fairly steady: 89.0% in Jul–Sep 2025, 82.0% in Oct–Dec 2025, 81.4% in Jan–Mar 2026 and 88.6% in Apr–Jun 2026. A spread of 8 points is about what a sample of this size moves on its own, so the annual figure is a fair summary.

Across the week, Tuesday is the strongest day at 88.5% on time and Friday the weakest at 78.0%. 11 points is a smaller lever than departure hour, but it is free.

Delay causes

Why Delta runs late on this route

One category carries most of the weight here. Carrier accounts for 77% of the 4,344 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.

Carrier
77%
National Airspace System
18%
Late-arriving aircraft
4%
Extreme weather
1%

The largest share of delay minutes, 77%, 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 3,349 of the 4,344 delay minutes reported here. The split is drawn from 4,344 reported delay minutes.

Cancellations sit at 1.65% against a national 1.81%, which is ordinary. Diversions add another 1.10%.

Connections and stage length

What a delay here costs

Badly late arrivals are rare here: only 4.5% 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 76.6% on time across 364 flights, 9 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 9 points of difference.

One caution: this is a thin sample. 364 flights over twelve months is enough to clear this site's floor but not enough to pin the rate down tightly, and a single bad week moves it by more than a point. Treat the grade as a rough reading.

What to do with this

Booking Delta on MCI to SEA

Put together: treat all of this as provisional. 364 flights over twelve months is enough to clear this site's floor and not enough to be confident to better than a couple of points. The 85.3% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 354 completed flights over 12 months sit behind that.

Where to go next

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.

Key figures