Flight number record
AS 305
Alaska Airlines · Miami to Seattle
- Route
- MIA → SEA
- Departs
- 18:20
- Flights
- 281
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s AS 305, check with Alaska Airlines.
AS 305 draws a C. About one flight in three arrives at least 15 minutes late, and the typical late arrival is roughly 45 minutes behind schedule. Build slack into anything you connect to. That rests on 281 flights, with a median arrival 1 minute late.
The national on-time rate over the same period is 77.3%, so AS 305 runs 10 points behind the country as a whole. Across a thousand flights that is about 97 extra late arrivals.
Key figures
On time
67.6%
Arrivals under 15 minutes late, of 275 completed flights
Avg delay
47 min
Across delayed arrivals only, not all flights
Cancelled
1.42%
National rate is 1.89%
1 hour+ late
6.5%
National rate is 8.3%
These figures cover 281 flights between September 2025 and August 2026. On-time means an arrival less than 15 minutes after the scheduled gate time, the same threshold the Department of Transportation uses in its own reports. Cancelled and diverted flights are excluded from the on-time rate and counted separately, which is why the cancellation column matters on its own.
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Schedule
When AS 305 flies
AS 305 flies MIA to SEA without a single fixed slot. Its most common scheduled departure was 18:20, used on 70 of 281 flights, with 18:34 (52 flights) and 18:04 (45 flights) next.
- Departs 18:2070 flights24.9%
- Departs 18:3452 flights18.5%
- Departs 18:0445 flights16.0%
Scale runs 0% to 100%.
Share of scheduled departures at each local time. Times used on fewer than one flight in ten are not listed.
A 18:20 departure sits in the 5pm–8pm window. Across every US flight scheduled in that window the on-time rate is 68.0%, and AS 305 runs level with that at 67.6%. By that time of day most aircraft have flown several legs already, and whatever went wrong earlier is still in the schedule.
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Against the route
AS 305 next to MIA to SEA
Every carrier on MIA to SEA combined arrived on time 68.7% of the time across 1,233 flights, so AS 305 is about level with it. Across its whole network Alaska Airlines managed 79.7%, which this flight trails by 12 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| AS 305thin sample | 281 | 67.6% | 47 min | 1.42% | C |
| All Alaska Airlines on MIA–SEA | 392 | 69.1% | 48 min | 1.28% | C |
| All carriers on MIA–SEA | 1,233 | 68.7% | 64 min | 1.05% | C |
| Alaska Airlines, whole network | 309,844 | 79.7% | 52 min | 1.20% | B |
Across the year
AS 305 quarter by quarter
AS 305 did not run the same all year. Its best quarter was Apr–Jun 2026 at 74.2% on time and its weakest Oct–Dec 2025 at 59.5%, a swing of 15 points on roughly 70 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.
- Oct–Dec 202538 flights59.5%
- Jan–Mar 202690 flights61.4%
- Apr–Jun 202691 flights74.2%
- Jul–Sep 202662 flights72.1%
Scale runs 50% to 80%.
By weekday, AS 305 did best on Tuesday at 76.3% on time and worst on Friday at 58.5%. Each day rests on about 40 flights, so a gap of 18 points is worth noticing but could still narrow in another year.
Arrival by arrival
How late AS 305 runs when it is late
AS 305 often beats the schedule: 73 of 275 completed flights, 27%, arrived 15 minutes or more early. The 89 late arrivals split 41 under half an hour, 30 between 30 and 60 minutes, and 18 an hour or more.
- 15+ min early73 flights26.5%
- Within 15 min113 flights41.1%
- 15–29 min late41 flights14.9%
- 30–59 min late30 flights10.9%
- 1–2 hours late9 flights3.3%
- 2+ hours late9 flights3.3%
Scale runs 0% to 100%.
Share of 275 completed flights by arrival against schedule.
24 of 83 late departures made up the time and arrived on time, 29% of them. In the other direction, 30 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 AS 305
The latest arrival of the period was on 14 December 2025, 3 hours 2 minutes behind schedule; most of its delay minutes were filed as a late-arriving aircraft. The five worst days are spread across December, April, August, March and November, with no single month standing out.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 14 December 2025 | 3 hours 2 minutes | Late-arriving aircraft |
| 26 April 2026 | 3 hours 2 minutes | Extreme weather |
| 30 August 2026 | 2 hours 54 minutes | Late-arriving aircraft |
| 5 March 2026 | 2 hours 25 minutes | Carrier |
| 28 November 2025 | 2 hours 19 minutes | Carrier |
Delay causes
Why AS 305 runs late
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 4,186 reported delay minutes.
- 38%Late-arriving aircraft
- 28%Carrier
- 28%National Airspace System
- 6%Extreme weather
38% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 4,186 reported delay minutes here, that single category outweighs weather by 6 to one. The split is drawn from 4,186 delay minutes reported on AS 305.
Cancellations sit at 1.42% against a national 1.89%, which is ordinary. Diversions add another 0.71%.
Connections and routes
What a delay on this flight costs
6.5% of arrivals land an hour or more late, close to the national 8.3%, so a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last roughly 45 minutes, which a normal layover absorbs.
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.
AS 305 is not only a MIA to SEA flight. It also flew SEA to MIA (264 flights, 79.1% on time) often enough to be scored on its own. Airlines attach one number to several legs of an aircraft's day, and each leg keeps its own record here, so check which city pair is on your booking before reading a rate.
One caution: this is a thin sample. 281 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.
| Also flown as | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| SEA to MIAthin sample | 264 | 79.1% | 40 min | 0.00% | B+ |
What to do with this
Booking AS 305
For a booking, read AS 305 as 67.6% on time with 1.42% cancelled over 281 flights. Those are rates from the past twelve months, not a forecast for any particular day.
Related
Where to go next
- MIA to SEA, every carrier and departure
- SEA to MIA, the return direction
- Delta Air Lines 506 on the same route61.2%
- Miami International (MIA) delay statistics
- Seattle-Tacoma International (SEA) delay statistics
- Alaska Airlines on-time record
- Every Alaska Airlines flight number with a record
- The most and least reliable flight numbers in the US
- Why the first flight of the morning is statistically safest
A flight number here means Alaska Airlines’s own number as it reports to the DOT. How the figures are computed is on the methodology page.
Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.