Carrier route record

DLMCI→SEA

Delta Air Lines · Kansas City to Seattle

Flights: 364
Period: September 2025 to August 2026
Share of route: 32%
Carriers: 3

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

Delta on MCI to SEA earns an A. Close to nine flights in ten arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 10 points better than the national rate of 77.3%. When something does go wrong the average delay runs a little over an hour. That rests on 364 flights, with a median arrival 8 minutes early.

Set against the rest of the country, Delta's MCI to SEA record is 10 points better than the US average of 77.3%. That gap is worth roughly 97 fewer late arrivals for every thousand flights.

On time

87.0%

Arrivals under 15 minutes late, of 354 completed flights

Avg delay

75 min

Across delayed arrivals only, not all flights

Cancelled

1.65%

National rate is 1.89%

Whole route

85.0%

Every carrier on MCI to SEA, 1,126 flights

These figures cover 364 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

Delta against every carrier on MCI to SEA

Delta flew 364 of the 1,126 flights on MCI to SEA, about 32% of it. Its 87.0% on time is 2 points better than the route as a whole, which runs 85.0%. Ranked by on-time rate it is first of three carriers on the route, where the range runs from Delta at 87.0% to Southwest at 58.8%. 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	87.0%	75 min	1.65%	A
Alaska Airlines	745	84.7%	63 min	0.67%	B+
Southwest Airlinesthin sample	17	58.8%	37 min	0.00%	D+

Flight by flight

Delta flight numbers on MCI to SEA

DL 210507:0087.0% · 364 flights

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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–8am253 flights89.5%
8am–11am111 flights81.3%
11am–2pm—
2pm–5pm—
5pm–8pm—
8pm–5am—

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

Book the early departure. Flights leaving between 5am–8am arrive on time 89.5% of the time, against 81.3% for the morning window. That is 8 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 253 flights scheduled in it.

Across the year

Delta on MCI to SEA through the year

Jul–Sep 202530 flights—
Oct–Dec 202591 flights82.0%
Jan–Mar 202690 flights81.4%
Apr–Jun 202691 flights88.6%
Jul–Sep 202662 flights96.8%

Scale runs 75% to 100%. 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 87.0% on time across 364 flights.

Delta on MCI to SEA did not run the same all year. Its best quarter was Jul–Sep 2026 at 96.8% on time and its weakest Jan–Mar 2026 at 81.4%, a swing of 15 points on roughly 91 flights a quarter. The twelve-month rate averages over that, so if you are flying in a weak quarter the quarter's own figure is the better guide.

Across the week, Monday is the strongest day at 88.5% on time and Friday the weakest at 82.0%, a spread of 7 points.

Arrival by arrival

How late Delta on MCI to SEA runs when it is late

Delta on MCI to SEA often beats the schedule: 125 of 354 completed flights, 35%, arrived 15 minutes or more early. Most of the lateness is short. 24 of the 46 late arrivals were under half an hour behind, and 11 reached an hour or more.

15+ min early125 flights35.3%
Within 15 min183 flights51.7%
15–29 min late24 flights6.8%
30–59 min late11 flights3.1%
1–2 hours late6 flights1.7%
2+ hours late5 flights1.4%

Scale runs 0% to 100%.

Share of 354 completed flights by arrival against schedule.

A late pushback is often recovered here: of 28 departures that left 15 minutes late or more, 9 still arrived on time. In the other direction, 27 flights left on time yet arrived 15 minutes late or more, so that delay built up after pushback: in the air, in a holding pattern or on the ground at SEA.

The worst days

Worst days for Delta on MCI to SEA

The latest arrival of the period was on 24 October 2025, 10 hours 19 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). The same cause led on four of the five worst days.

The latest arrivals of Delta on MCI to SEA in the period
Date	Arrived late by	Largest filed cause
24 October 2025	10 hours 19 minutes	Carrier
30 January 2026	7 hours 52 minutes	Carrier
5 September 2025	5 hours 57 minutes	Carrier
12 December 2025	5 hours 46 minutes	Late-arriving aircraft
11 April 2026	3 hours 30 minutes	Carrier

Delay causes

Why Delta runs late on this route

Carrier accounts for 72% of the 3,428 delay minutes carriers reported here, and the remaining four split what is left.

Carrier
72%
National Airspace System
22%
Late-arriving aircraft
6%
Extreme weather
1%

The largest share of delay minutes, 72%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 2,451 of the 3,428 delay minutes reported here. The split is drawn from 3,428 reported delay minutes.

Cancellations sit at 1.65% against a national 1.89%, which is ordinary. Diversions add another 1.10%.

Connections and stage length

What a delay here costs

Badly late arrivals are rare here: only 3.1% land an hour or more behind schedule, against 8.3% 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.

The return leg is a different operation and performs like one: it runs 77.4% on time across 364 flights, 10 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 10 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 87.0% 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, September 2025 to August 2026. Last updated 22 October 2026; recomputed monthly. How this data is collected.

Key figures