Flight number record

AS 377

Alaska Airlines · Atlanta to Seattle

Route: ATL → SEA
Departs: 07:00
Flights: 302
Period: September 2025 to August 2026

Historical statistics for September 2025 to August 2026, not live status. For today’s AS 377, check with Alaska Airlines.

AS 377 earns an A+. More than four flights in five arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 8 points better than the national rate of 77.3%. When something does go wrong the average delay runs a little over an hour. That rests on 302 flights, with a median arrival 8 minutes early.

Set against the rest of the country, AS 377's record is 8 points better than the US average of 77.3%. That gap is worth roughly 80 fewer late arrivals for every thousand flights.

On time

85.3%

Arrivals under 15 minutes late, of 300 completed flights

Avg delay

72 min

Across delayed arrivals only, not all flights

Cancelled

0.66%

National rate is 1.89%

1 hour+ late

4.0%

National rate is 8.3%

These figures cover 302 flights between September 2025 and August 2026. The median arrival is 8 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.

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Schedule

When AS 377 flies

AS 377 flies ATL to SEA without a single fixed slot. Its most common scheduled departure was 07:00, used on 153 of 302 flights, with 07:50 (36 flights) and 07:20 (36 flights) next.

Departs 07:00153 flights50.7%
Departs 07:5036 flights11.9%
Departs 07:2036 flights11.9%

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 07:00 departure sits in the 5am–8am window. Across every US flight scheduled in that window the on-time rate is 89.3%, and AS 377 runs 4 points worse at 85.3%. Early departures usually start with an aircraft that has not flown yet that day, which is most of why the window does well.

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Against the route

AS 377 next to ATL to SEA

Every carrier on ATL to SEA combined arrived on time 76.7% of the time across 3,297 flights, so AS 377 is 9 points ahead of it. Alaska flew 893 flights on the same city pair under all its flight numbers, including this one, and those ran 76.4% on time. Across its whole network Alaska Airlines managed 79.7%, which this flight beats by 6 points.

AS 377 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
AS 377thin sample	302	85.3%	72 min	0.66%	A+
All Alaska Airlines on ATL–SEA	893	76.4%	55 min	1.01%	B
All carriers on ATL–SEA	3,297	76.7%	57 min	0.73%	B+
Alaska Airlines, whole network	309,844	79.7%	52 min	1.20%	B

Across the year

AS 377 quarter by quarter

AS 377 did not run the same all year. Its best quarter was Jul–Sep 2026 at 95.6% on time and its weakest Jan–Mar 2026 at 74.4%, a swing of 21 points on roughly 76 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 202521 flights—
Oct–Dec 202554 flights81.5%
Jan–Mar 202690 flights74.4%
Apr–Jun 202691 flights91.1%
Jul–Sep 202646 flights95.6%

Scale runs 65% to 100%. Rows with fewer than 30 flights show a dash.

By weekday, AS 377 did best on Wednesday at 93.5% on time and worst on Sunday at 75.6%. Each day rests on about 43 flights, so a gap of 18 points is worth noticing but could still narrow in another year.

Arrival by arrival

How late AS 377 runs when it is late

AS 377 often beats the schedule: 108 of 300 completed flights, 36%, arrived 15 minutes or more early. The 44 late arrivals split 20 under half an hour, 12 between 30 and 60 minutes, and 12 an hour or more.

15+ min early108 flights36.0%
Within 15 min148 flights49.3%
15–29 min late20 flights6.7%
30–59 min late12 flights4.0%
1–2 hours late7 flights2.3%
2+ hours late5 flights1.7%

Scale runs 0% to 100%.

Share of 300 completed flights by arrival against schedule.

A late pushback is often recovered here: of 39 departures that left 15 minutes late or more, 12 still arrived on time. In the other direction, 17 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 377

The latest arrival of the period was on 30 April 2026, 12 hours 57 minutes behind schedule; most of its delay minutes were filed as a late-arriving aircraft. The five worst days are spread across April, September, January, October and March, with no single month standing out.

The latest arrivals of AS 377 in the period
Date	Arrived late by	Largest filed cause
30 April 2026	12 hours 57 minutes	Late-arriving aircraft
26 September 2025	3 hours 56 minutes	Carrier
25 January 2026	3 hours 43 minutes	Late-arriving aircraft
13 October 2025	3 hours 18 minutes	Carrier
16 March 2026	2 hours 44 minutes	Extreme weather

Delay causes

Why AS 377 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 3,183 reported delay minutes.

Late-arriving aircraft
37%
Carrier
31%
National Airspace System
26%
Extreme weather
5%
Security
1%

37% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 3,183 reported delay minutes here, that single category outweighs weather by 7 to one. The split is drawn from 3,183 delay minutes reported on AS 377.

Cancellations are rare at 0.66%, below the national 1.89% 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 routes

What a delay on this flight costs

Badly late arrivals are rare here: only 4.0% land an hour or more behind schedule, against 8.3% nationally. Connections built on this flight are about as safe as US domestic connections get, though a cancelled flight still ignores every layover you give it.

At 2,182 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 one other city pair in the data, including MSO to SEA (26), but none flew often enough under AS 377 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to ATL to SEA only.

One caution: this is a thin sample. 302 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 377

For a booking, AS 377 has one of the better records a US domestic flight can show: 85.3% on time and 0.66% cancelled. That is a base rate, not a promise about any single 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, September 2025 to August 2026. Last updated 22 October 2026; recomputed monthly. How this data is collected.

Key figures