79% of flights from Seattle to Miami arrived on time over the past 12 months. That is about the typical U.S. route. The 7 a.m. departures ran on time 86% of the time; the 10 p.m. ones 73%. Most reliable airline: Alaska Airlines (80%). 6% of flights arrived more than an hour late or not at all.
How late?
The on-time rate treats a flight 20 minutes late the same as one 5 hours late. Here's the split for SEA → MIA: when a flight was late, it was under 45 minutes late 64% of the time. About 1 in 20 flights landed an hour or more late, and 1 in 82 three hours or more; 0.8% were cancelled outright.
- On time or early79%
- 15–30 min late8.3%
- 30–60 min late6.7%
- 1–2 hours late3.1%
- 2–3 hours late0.6%
- 3+ hours late1.2%
- Diverted0.6%
- Cancelled0.8%
Share of all 1,231 scheduled flights, past 12 months, by arrival time against schedule.
By airline
| Airline | Flights | On time | Cancelled | Typical arrival | 1h+ late | Avg when late | Operated by |
|---|---|---|---|---|---|---|---|
| American Airlines | 475 | 77% | 0.8% | −8 min | 6.1% | +68 min | American Airlines |
| Alaska Airlines | 391 | 80% | 0.3% | −9 min | 3.1% | +40 min | Alaska Airlines |
| Delta Air Lines | 365 | 79% | 1.4% | −8 min | 5.5% | +65 min | Delta Air Lines |
Airline = the name on the ticket. Regional flights (e.g. "Delta Connection") count under the ticketing airline, and the operator is listed.
Best time of day to fly
On-time rate by scheduled departure hour (local time at SEA). Delays build through the day as late planes knock on, so early flights usually do best.
By airline and hour
| Departs | American Airlines | Alaska Airlines | Delta Air Lines |
|---|---|---|---|
| 7 a.m. | — | — | 84% |
| 8 a.m. | — | 78% | 76% |
| 8 p.m. | 79% | — | — |
| 10 p.m. | 73% | — | — |
Last flight of the day
On SEA → MIA, each airline's last flight of the day was cancelled 0.0% of the time, against 0.7% for its earlier flights, so here the last flight is actually the safer one. It arrived 3+ hours late 0.7% of the time (earlier flights: 1.5%). It matters more than the numbers suggest. Miss an earlier flight and there's another one that evening; miss the last one and you're usually waiting until morning.
| Airline | Last departure | Last: cancelled | Last: 3h+ late | Earlier: cancelled | Next morning |
|---|---|---|---|---|---|
| American Airlines | 8:45 p.m. | 0.0% | 0.9% | 0.9% | first flight 12:58 p.m. |
Last flight = the airline's last scheduled departure on this route that day, on days it flies the route at least twice; past 12 months. Times are typical scheduled times over the latest three months.
By month
Each calendar month pooled over 2023–2026. Best: October (87%). Worst: January (70%).
By day of week
| Day | Flights | On time | Cancelled |
|---|---|---|---|
| Monday | 178 | 75% | 1.7% |
| Tuesday | 174 | 82% | 0.6% |
| Wednesday | 172 | 84% | 0.6% |
| Thursday | 176 | 82% | 0.6% |
| Friday | 177 | 73% | 1.1% |
| Saturday | 177 | 75% | 0.0% |
| Sunday | 177 | 79% | 1.1% |
Why flights were late
Share of delay minutes on flights 15+ minutes late, as reported to BTS by the airlines.
Cancellations: airline 6 · weather 3 · air traffic/airport 1
Month by month
Flight numbers on this route
Regular flights with at least 120 scheduled trips in the past year. Sorted by departure time.
| Flight | Departs | Flights | On time | Cancelled | Typical arrival | Operated by |
|---|---|---|---|---|---|---|
| DL 506 | 8:00 a.m. | 365 | 79% | 1.4% | −8 min | Delta Air Lines |
| AS 305 | 8:12 a.m. | 264 | 79% | 0.0% | −5 min | Alaska Airlines |
| AA 1471 | 8:45 p.m. | 209 | 76% | 0.0% | −6 min | American Airlines |
Worst days in the past year
| Date | Flights | On time | Cancelled |
|---|---|---|---|
| Dec 27, 2025 | 5 | 0% | 0 |
| Nov 24, 2025 | 4 | 0% | 0 |
| Jul 1, 2026 | 4 | 0% | 0 |
| Feb 21, 2026 | 3 | 0% | 0 |
| Mar 30, 2026 | 3 | 0% | 0 |
Nearby airport alternatives
Other ways to make the same trip, using airports within 60 miles of Seattle or Miami. None has been clearly more reliable than SEA → MIA.
| Route | Flights | On time | Cancelled |
|---|---|---|---|
| SEA → MIA (this route) | 1,231 | 79% | 0.8% |
| SEA → FLL Seattle-Tacoma to Fort Lauderdale | 826 | 78% | 0.7% |
Questions
How often are flights from SEA to MIA on time?
79% of 1,231 scheduled flights from Seattle, WA to Miami, FL arrived within 15 minutes of schedule between September 2025 and August 2026. 0.8% were cancelled.
What is the best time of day to fly SEA to MIA?
Flights scheduled to leave at 7 a.m. were the most reliable (86% on time). The 10 p.m. departures were the least (73%).
Which airline is most on time from SEA to MIA?
Alaska Airlines: 80% of its 391 flights on the route arrived on time. American Airlines: 77%. Delta Air Lines: 79%.
What month has the most delays from SEA to MIA?
January (70% on time). The best month is October (87%), over 2023–2026.
Is the last flight of the day from SEA to MIA more likely to be cancelled?
No, the opposite. Each airline's last SEA–MIA flight of the day was cancelled 0.0% of the time over the past year, against 0.7% for its earlier flights. If the last flight is cancelled, the next one is usually the following morning.
Related
- MIA → SEA (return)
- Seattle-Tacoma (SEA) delays by hour
- Flights into Miami (MIA)
- American Airlines on-time record
- Alaska Airlines on-time record
- Delta Air Lines on-time record
- Connecting off this flight? Check the risk
Domestic flights by the airlines that report to the U.S. DOT, plus their regional partners. "On time" means arriving less than 15 minutes after schedule; cancelled and diverted flights count as not on time. Past performance is a guide, not a forecast. Method.