Route on-time record

SEA to BOS: most on-time flights and the best time to fly

Seattle (Seattle–Tacoma International Airport) to Boston (Boston Logan International Airport). 2,436 nonstop flights in Jun 2025 to May 2026, 74% arrived within 15 minutes and 1.1% were cancelled. The most reliable flight number was Alaska 330 at 7:55 AM.

Flying on a specific date? We’ll adjust for the month, the weekday and the forecast.

SEA → BOS

Seattle to Boston: 2,436 nonstop flights a year

On time (12 months)

74%

Cancelled

1.1%

avg delay 19 min

Best time to leave

Before 9 AM

82% on time vs 59% 9 AM to noon

Most reliable airline

Delta

80% chance on time

Check SEA to BOS fares

Lowest nonstop fare seen in the next two months: $151 (Alaska 460 on 2026-10-20). Fares open on our travel partner (Aviasales). Pick the flight number you chose here.

Most reliable nonstop flights

Ranked by the chance the flight operates and arrives within 15 minutes of schedule, from Jun 2025 to May 2026 records.

#1 · Alaska 330
7:55 AM → 4:32 PM5h 37m nonstop
Local times, typical schedule. Last flown 2026-05-31.
86%
chance on time
On time (history)
95%
Cancelled
0.0%
Avg arrival delay
5 min
- Arrived on time 95% of the time (19 flights, Jun 2025 to May 2026).
- Leaves in this route's most on-time window (Before 9 AM: 82% on time; 9 AM to noon: 59%).
- Departs outside SEA's trouble window (4 PM to 10 PM, when 54% of its 68 ground stops and delay programs started).
- Lands inside BOS's trouble window: 79% of its 196 ground stops and delay programs started between noon and 6 PM.
Limited track record · 19 flights
Find Alaska 330 fares Opens this date on Aviasales
#2 · Delta 459
7:15 AM → 3:42 PM5h 27m nonstop
Local times, typical schedule. Last flown 2026-05-31.
86%
chance on time
On time (history)
88%
Cancelled
2.2%
Avg arrival delay
12 min
- Arrived on time 88% of the time (355 flights, Jun 2025 to May 2026).
- Leaves in this route's most on-time window (Before 9 AM: 82% on time; 9 AM to noon: 59%).
- Departs outside SEA's trouble window (4 PM to 10 PM, when 54% of its 68 ground stops and delay programs started).
- Lands inside BOS's trouble window: 79% of its 196 ground stops and delay programs started between noon and 6 PM.
Strong track record · 355 flights
Find Delta 459 fares Opens this date on Aviasales
#3 · Alaska 1436
7:00 AM → 3:33 PM5h 33m nonstop
Local times, typical schedule. Last flown 2026-05-12.
83%
chance on time
On time (history)
87%
Cancelled
0.0%
Avg arrival delay
5 min
- Arrived on time 87% of the time (15 flights, Jun 2025 to May 2026).
- Leaves in this route's most on-time window (Before 9 AM: 82% on time; 9 AM to noon: 59%).
- Departs outside SEA's trouble window (4 PM to 10 PM, when 54% of its 68 ground stops and delay programs started).
- Lands inside BOS's trouble window: 79% of its 196 ground stops and delay programs started between noon and 6 PM.
Limited track record · 15 flights
Find Alaska 1436 fares Opens this date on Aviasales
#4 · Delta 412
11:15 AM → 7:49 PM5h 34m nonstop
Local times, typical schedule. Last flown 2026-05-31.
78%
chance on time
On time (history)
92%
Cancelled
0.0%
Avg arrival delay
7 min
- Arrived on time 92% of the time (25 flights, Jun 2025 to May 2026).
- Leaves in this route's least on-time window (9 AM to noon: 59% on time; Before 9 AM: 82%).
- Departs outside SEA's trouble window (4 PM to 10 PM, when 54% of its 68 ground stops and delay programs started).
- Short track record (25 flights), so its score leans on the airline's record at this hour.
Limited track record · 25 flights
Find Delta 412 fares Opens this date on Aviasales
#5 · Delta 473
10:25 PM → 6:50 AM5h 25m nonstop
Local times, typical schedule. Last flown 2026-05-31.
78%
chance on time
On time (history)
80%
Cancelled
1.7%
Avg arrival delay
10 min
- Arrived on time 80% of the time (357 flights, Jun 2025 to May 2026).
- Departs outside SEA's trouble window (4 PM to 10 PM, when 54% of its 68 ground stops and delay programs started).
Strong track record · 357 flights
Find Delta 473 fares Opens this date on Aviasales
#6 · Delta 474
3:45 PM → 11:59 PM5h 19m nonstop
Local times, typical schedule. Last flown 2026-05-31.
76%
chance on time
On time (history)
75%
Cancelled
0.4%
Avg arrival delay
23 min
- Arrived on time 75% of the time (221 flights, Jun 2025 to May 2026).
- Departs outside SEA's trouble window (4 PM to 10 PM, when 54% of its 68 ground stops and delay programs started).
Strong track record · 221 flights
Find Delta 474 fares Opens this date on Aviasales
#7 · Alaska 214
10:15 PM → 6:39 AM5h 24m nonstop
Local times, typical schedule. Last flown 2026-04-20.
76%
chance on time
On time (history)
81%
Cancelled
0.0%
Avg arrival delay
9 min
- Arrived on time 81% of the time (54 flights, Jun 2025 to May 2026).
- Never cancelled in 54 scheduled flights.
- Departs outside SEA's trouble window (4 PM to 10 PM, when 54% of its 68 ground stops and delay programs started).
- Short track record (54 flights), so its score leans on the airline's record at this hour.
Limited track record · 54 flights
Find Alaska 214 fares Opens this date on Aviasales
#8 · Alaska 460
3:38 PM → 11:59 PM5h 21m nonstop
Local times, typical schedule. Last flown 2026-05-31.
75%
chance on time
On time (history)
77%
Cancelled
1.1%
Avg arrival delay
12 min
- Arrived on time 77% of the time (351 flights, Jun 2025 to May 2026).
- Departs outside SEA's trouble window (4 PM to 10 PM, when 54% of its 68 ground stops and delay programs started).
Strong track record · 351 flights
Find Alaska 460 fares Opens this date on Aviasales
#9 · Alaska 536
10:45 PM → 7:12 AM5h 27m nonstop
Local times, typical schedule. Last flown 2026-05-31.
72%
chance on time
On time (history)
71%
Cancelled
0.8%
Avg arrival delay
13 min
- Arrived on time 71% of the time (245 flights, Jun 2025 to May 2026).
- Departs outside SEA's trouble window (4 PM to 10 PM, when 54% of its 68 ground stops and delay programs started).
Strong track record · 245 flights
Find Alaska 536 fares Opens this date on Aviasales
#10 · Alaska 306
8:42 AM → 5:05 PM5h 28m nonstop
Local times, typical schedule. Last flown 2026-05-31.
71%
chance on time
On time (history)
73%
Cancelled
1.4%
Avg arrival delay
16 min
- Arrived on time 73% of the time (360 flights, Jun 2025 to May 2026).
- Leaves in this route's most on-time window (Before 9 AM: 82% on time; 9 AM to noon: 59%).
- Departs outside SEA's trouble window (4 PM to 10 PM, when 54% of its 68 ground stops and delay programs started).
- Lands inside BOS's trouble window: 79% of its 196 ground stops and delay programs started between noon and 6 PM.
Strong track record · 360 flights
Find Alaska 306 fares Opens this date on Aviasales

Airlines on this route

Season-adjusted chance of operating and arriving on time.

Delta Air Lines80%
978 flights · 82% on time as flown · 1.5% cancel
Alaska Airlines72%
1,210 flights · 72% on time as flown · 1.0% cancel
JetBlue65%
248 flights · 57% on time as flown · 0.7% cancel

On time by departure time

All airlines, scheduled local departure, Jun 2025 to May 2026.

Before 9 AM82%
681 flights · avg delay 13 min
9 AM to noon59%
394 flights · avg delay 29 min
3 to 6 PM76%
588 flights · avg delay 16 min
After 9 PM74%
748 flights · avg delay 20 min

Best day: Tuesday (79%). Worst: Thursday (72%).

On time by month

All airlines, Jun 2023 to May 2026. Several years per month, so one stormy season doesn't define a month. Travel-month estimates use this seasonal pattern.

What delays this route

Airline (crew, maintenance, boarding)37%
Air traffic control and airport volume32%
Late-arriving aircraft24%
Severe weather6%

Share of delay minutes by the cause airlines report to the US DOT.

Historical odds, not a guarantee. Built from the US DOT Bureau of Transportation Statistics on-time reports (Jun 2025 to May 2026), FAA ground stop and delay program advisories, and 20 years of airport weather observations. Covers US airlines that report to the DOT; schedules are flights operated recently, so confirm times when you book. ATIS Alerts is not affiliated with any airline. Fares are what Aviasales travelers saw in recent searches (USD, one way, 1 adult), not live quotes; the partner site shows the current price. Fare links go to our travel partner and may earn us a commission at no cost to you. Affiliate disclosure

SEA to BOS questions

What time of day is best to fly SEA to BOS?: Before 9 AM: 82% of flights arrived on time, against 59% for departures 9 AM to noon. Later flights inherit delays from earlier ones, so the first departures of the day usually run best.
Which airline is most on time from SEA to BOS?: Delta, with a season-adjusted 80% chance of operating and arriving on time over 978 flights. The adjustment compares each airline with what the route did in the months it flew, so a carrier that skipped a stormy month gets no free credit.
What is the worst month for delays on SEA to BOS?: June (67% on time); the best was November (84%), averaged over Jun 2023 to May 2026.
Is this a prediction for my flight?: No. These are historical odds from the US DOT on-time reports, FAA advisories and airport weather records. Check your flight status and the FAA delay board on the day you fly.

More routes from SEA

Live status: FAA delays and ground stops

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