Route reliability record
MSP→SEA
Minneapolis to Seattle
- Flights
- 2,690
- Period
- July 2025 to June 2026
- Distance
- 1,399 mi
- Carriers
- 2
This route lands a B, 4 points better than the national rate of 77.6%. About one flight in five arrive 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 2,690 flights, of which Delta Air Lines flew 1,737 at 82.1% on time.
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
81.1%
Arrivals under 15 minutes late, of 2,656 completed flights
Avg delay
58 min
Across delayed arrivals only, not all flights
Cancelled
1.04%
National rate is 1.81%
Best carrier
Delta
82.1% on time across 1,737 flights
These figures cover 2,690 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 MSP to SEA
The two carriers here are closely matched: 3 points separate the best from the worst. At that spread, schedule and price are better tie-breakers than reliability. Sample sizes are shown so you can see which rows are worth weighing.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Delta Air Lines | 1,737 | 82.1% | 60 min | 0.92% | B+ |
| Alaska Airlines | 953 | 79.4% | 56 min | 1.26% | B |
No carrier stands out. Delta tops the table at 82.1%, 3 points clear of the bottom, which is inside the range this kind of sample moves year to year.
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 14 points, against 3 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am463 flights87.6%
- 8am–11am551 flights87.5%
- 11am–2pm212 flights84.0%
- 2pm–5pm658 flights74.1%
- 5pm–8pm533 flights75.0%
- 8pm–5am273 flights84.0%
Scale runs 65% to 95%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 87.6% of the time, against 74.1% for the afternoon window. That is 14 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 2pm–5pm window is the busiest, with 658 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 41 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 52.2% on time, against 93.3% in April. 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 295 flights.
The day of the week is close to irrelevant here: 3 points separates the best day from the worst. Weekly demand peaks are not what drives the delays on this operation.
Delay causes
Why this route gets delayed
One category carries most of the weight here. Carrier accounts for 43% of the 29,000 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.
- 43%Carrier
- 27%Late-arriving aircraft
- 26%National Airspace System
- 5%Extreme weather
- 0%Security
The largest share of delay minutes, 43%, 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 12,000 of the 29,000 delay minutes reported here. The split is drawn from 29,268 reported delay minutes.
Cancellations sit at 1.04% against a national 1.81%, which is ordinary. Diversions add another 0.22%.
Connections and stage length
What a delay here actually costs
5.4% 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 are the about an hour kind, which a normal layover absorbs.
The 1,399 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 85.5% on time across 2,689 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 2,690 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.
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 93.3% on time and December 52.2%, a swing of 41 points. If the dates move at all, move them out of December before you think about anything else. 2,656 completed flights over 12 months sit behind that.
Common questions
MSP to SEA questions
How often is MSP to SEA delayed?
About one flight in five arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 18.9% of the 2,690 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on MSP to SEA?
Delta Air Lines leads at 82.1% on time across 1,737 flights. Alaska Airlines is at the other end on 79.4%, a gap of 3 points. Sample size matters as much as the percentage: a rate built from a few hundred flights moves around far more than one built from ten thousand.
What time of day has the fewest delays on MSP to SEA?
The 5am–8am departure window is the strongest at 87.6% on time. The 2pm–5pm window is the weakest at 74.1%, 14 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 MSP to SEA?
December is the weakest month at 52.2% on time, compared with 93.3% in April. Across the year that is 41 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 MSP — the return legseparate record
- Minneapolis-St Paul International (MSP) delay statistics
- Seattle-Tacoma International (SEA) delay statistics
- Delta Air Lines on-time record82.1%
- Alaska Airlines on-time record79.4%
- 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. MSP to SEA and SEA to MSP are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Updated monthly. How this data is collected.