Carrier route record
AAMIA→SEA
American Airlines · Miami to Seattle
- Flights
- 423
- Period
- July 2025 to June 2026
- Share of route
- 36%
- Carriers
- 3
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with American Airlines.
American on MIA to SEA sits in the middle of the pack with a C+. About seven flights in ten arrive on time by the DOT's definition, 8 points worse than the national rate of 77.6%. The late ones land about an hour behind schedule. That rests on 423 flights. The strongest carrier on the route with a full sample, Alaska Airlines, flew 392 at 65.4% on time.
The national on-time rate over the same period is 77.6%, so American on MIA to SEA runs 8 points behind the country as a whole. Across a thousand flights that is about 81 extra late arrivals.
Key figures
On time
69.5%
Arrivals under 15 minutes late, of 420 completed flights
Avg delay
56 min
Across delayed arrivals only, not all flights
Cancelled
0.47%
National rate is 1.81%
Whole route
65.7%
Every carrier on MIA to SEA, 1,180 flights
These figures cover 423 flights between July 2025 and June 2026. Beyond the headline rate, 11.0% of arrivals land a full hour or more behind schedule. That is the number that wrecks a connection, and it is not visible in an on-time percentage alone.
Carrier by carrier
American against every carrier on MIA to SEA
American flew 423 of the 1,180 flights on MIA to SEA, about 36% of it. Its 69.5% on time is 4 points better than the route as a whole, which runs 65.7%. Ranked by on-time rate it is first of three carriers on the route, where the range runs from American at 69.5% to Delta at 61.6%.
The two carriers here are closely matched: 4 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 |
|---|---|---|---|---|---|
| American Airlines (this page) | 423 | 69.5% | 56 min | 0.47% | C+ |
| Alaska Airlines | 392 | 65.4% | 50 min | 1.53% | C |
| Delta Air Lines | 365 | 61.6% | 93 min | 1.64% | D |
No carrier stands out. Alaska tops the table at 65.4%, 4 points clear of the bottom, which is inside the range this kind of sample moves year to year.
Departure window
When American runs best on this route
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 13 points, against 4 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am—
- 8am–11am58 flights79.3%
- 11am–2pm—
- 2pm–5pm—
- 5pm–8pm155 flights66.7%
- 8pm–5am210 flights68.9%
Scale runs 60% to 85%. Rows with fewer than 30 flights show a dash.
Book the morning departure. Flights leaving between 8am–11am arrive on time 79.3% of the time, against 66.7% for the evening window. That is 13 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 8pm–5am window is the busiest, with 210 flights scheduled in it.
Across the year
American on MIA to SEA through the year
January is the weak month at 51.5% on time, against 80.0% in June. 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. June was the busiest month here, with 60 flights.
Across the week, Tuesday is the strongest day at 80.0% on time and Saturday the weakest at 61.7%. 18 points is a smaller lever than departure hour, but it is free.
Delay causes
Why American runs late on this route
Carriers report a reason for every delay minute they cause, in five DOT categories. The split below is by minutes, not by number of flights, so a handful of very long weather delays weighs as much as many short ones. It covers 7,101 reported delay minutes.
- 41%Late-arriving aircraft
- 32%Carrier
- 21%National Airspace System
- 4%Extreme weather
- 2%Security
41% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. That is a cascade, and cascades start small and grow through the day. Across 7,101 reported delay minutes here, that single category outweighs weather by 10 to one. It is the strongest argument for booking the first departure of the morning, when the aircraft has been sitting at the gate overnight with nothing to inherit. The split is drawn from 7,101 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 79.3% on time here.
Cancellations are rare at 0.47%, 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 costs
For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 11.0% of arrivals land a full hour or more behind schedule, against 8.1% nationally. A 45-minute layover does not survive that, and no amount of walking quickly changes it. Ninety minutes is the honest minimum here, and two hours if the onward flight is on a separate ticket.
At 2,724 miles this is transcontinental flying, and long routes get a quiet structural advantage. Scheduled block time on a flight this length carries more padding in absolute minutes, so a twenty-minute late departure often still becomes an on-time arrival. Read the on-time rate here as slightly flattering next to a short-haul route with the same operational quality.
The return leg is a different operation and performs like one: it runs 75.1% on time across 423 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.
One caution: this is a thin sample. 423 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 American on MIA to SEA
Put together: treat all of this as provisional. 423 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 69.5% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 420 completed flights over 12 months sit behind that.
Related
Where to go next
- MIA to SEA, every carrier
- American on SEA to MIA, the return leg
- Alaska Airlines on MIA to SEA65.4%
- Delta Air Lines on MIA to SEA61.6%
- American Airlines network-wide record
- Miami International (MIA) delay statistics
- Seattle-Tacoma International (SEA) delay statistics
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
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.