Flight number record

AS 305

Alaska Airlines · Miami to Seattle

Route: MIA → SEA
Departs: 18:20
Flights: 257
Period: July 2025 to June 2026

Historical statistics for July 2025 to June 2026, not live status. For today’s AS 305, check with Alaska Airlines.

AS 305 draws a D. About one flight in three arrives at least 15 minutes late, and the typical late arrival is roughly 50 minutes behind schedule. Build slack into anything you connect to. That rests on 257 flights, with a median arrival 3 minutes late.

The national on-time rate over the same period is 77.6%, so AS 305 runs 14 points behind the country as a whole. Across a thousand flights that is about 135 extra late arrivals.

On time

64.1%

Arrivals under 15 minutes late, of 251 completed flights

Avg delay

51 min

Across delayed arrivals only, not all flights

Cancelled

1.56%

National rate is 1.81%

1 hour+ late

8.8%

National rate is 8.1%

These figures cover 257 flights between July 2025 and June 2026. Beyond the headline rate, 8.8% 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.

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 59 of 257 flights, with 18:34 (52 flights) and 18:04 (45 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.

Departs 18:2059 flights23.0%
Departs 18:3452 flights20.2%
Departs 18:0445 flights17.5%

Scale runs 0% to 100%. Rows with fewer than 30 flights show a dash.

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 68.2%, and AS 305 runs 4 points worse at 64.1%. By that time of day most aircraft have flown several legs already, and whatever went wrong earlier is still in the schedule.

Against the route

AS 305 next to MIA to SEA

Every carrier on MIA to SEA combined arrived on time 65.7% of the time across 1,180 flights, so AS 305 is 2 points behind it. Alaska flew 392 flights on the same city pair under all its flight numbers, including this one, and those ran 65.4% on time. Across its whole network Alaska Airlines managed 79.1%, which this flight trails by 15 points.

AS 305 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
AS 305thin sample	257	64.1%	51 min	1.56%	D
All Alaska Airlines on MIA–SEA	392	65.4%	50 min	1.53%	C
All carriers on MIA–SEA	1,180	65.7%	67 min	1.19%	C
Alaska Airlines, whole network	293,372	79.1%	52 min	1.28%	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 Jul–Sep 2025 at 51.4%, a swing of 23 points on roughly 64 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.

Jul–Sep 202538 flights51.4%
Oct–Dec 202538 flights59.5%
Jan–Mar 202690 flights61.4%
Apr–Jun 202691 flights74.2%

Scale runs 45% to 80%. Rows with fewer than 30 flights show a dash.

By weekday, AS 305 did best on Saturday at 73.0% on time and worst on Sunday at 58.3%. Each day rests on about 37 flights, so a gap of 15 points is worth noticing but could still narrow in another year.

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 4,603 reported delay minutes.

Late-arriving aircraft
37%
Carrier
33%
National Airspace System
26%
Extreme weather
5%

37% 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 4,603 reported delay minutes here, that single category outweighs weather by 7 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 4,603 delay minutes reported on AS 305.

Cancellations sit at 1.56% against a national 1.81%, which is ordinary. Diversions add another 0.78%.

Connections and routes

What a delay on this flight costs

8.8% 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 last roughly 50 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.

The same number turns up on two other city pairs in the data, including SEA to MIA (240) and PDX to SNA (9), but none flew often enough under AS 305 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to MIA to SEA only.

One caution: this is a thin sample. 257 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 AS 305

For a booking, read AS 305 as 64.1% on time with 1.56% cancelled over 257 flights. Those are rates from the past twelve months, not a forecast for any particular day.

Where to go next

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, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.

Key figures