Route reliability record
ATL→SEA
Atlanta to Seattle
- Flights
- 3,297
- Period
- September 2025 to August 2026
- Distance
- 2,182 mi
- Carriers
- 2
This route lands a B+, level with the national rate of 77.3%. About one flight in four arrives 15 minutes late or worse, and those flights are late by about an hour on average. That rests on 3,297 ATL to SEA flights, of which Delta Air Lines flew 2,404 at 76.8% on time.
Best time to fly ATL to SEA: a 5am–8am departure, ideally on a Saturday. Flights in that window arrived on time 82.5% of the time and Saturday flights 82.2%, against 76.7% for the route overall.
The US average over the same twelve months is 77.3%, so there is little to separate this route from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
76.7%
Arrivals under 15 minutes late, of 3,265 completed flights
Avg delay
57 min
Across delayed arrivals only, not all flights
Cancelled
0.73%
National rate is 1.89%
Best carrier
Delta
76.8% on time across 2,404 flights
These figures cover 3,297 flights between September 2025 and August 2026. The median arrival is 3 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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Carrier by carrier
Which airline is most reliable on ATL to SEA
The two carriers here are closely matched: half a point separate the best from the worst. At that spread, schedule and price are better tie-breakers than reliability. Sample sizes are shown so you can see which rows are worth weighing.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Delta Air Lines | 2,404 | 76.8% | 58 min | 0.62% | B+ |
| Alaska Airlines | 893 | 76.4% | 55 min | 1.01% | B |
No carrier stands out. Delta tops the table at 76.8%, half a point clear of the bottom, which is inside the range this kind of sample moves year to year.
Flight by flight
Flights on ATL to SEA
The flight numbers below flew this route at least 250 times in the period, busiest first. Each has its own record, with its schedule and delay causes.
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Best ways to make this trip
The most reliable ways to fly Atlanta to Seattle
Every airline on this route, ranked by how often a scheduled flight actually operated and arrived on time, with its best departure time and most punctual flight number. No nearby airport pair beat these.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. ATL → SEAAtlanta to Seattle | Delta Air Lines | 76.3% | 76.8% | 0.62% | 8am–11am, Sat | DL 774 09:40 |
| 2. ATL → SEAAtlanta to Seattle | Alaska Airlines | 75.6% | 76.4% | 1.01% | 5am–8am, Sat | AS 377 07:00 |
Success is the share of scheduled flights that operated and arrived less than 15 minutes late, so a cancelled flight counts against it. “(route)” means the best time comes from every carrier on the route rather than this airline alone.
Departure window
The best time of day to leave
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 19 points, against half a point between the best and worst carrier.
- 5am–8am650 flights82.5%
- 8am–11am646 flights81.2%
- 11am–2pm563 flights80.9%
- 2pm–5pm573 flights72.6%
- 5pm–8pm480 flights63.8%
- 8pm–5am385 flights75.7%
Scale runs 55% to 90%.
The 5pm–8pm window is where this operation falls apart: 63.8% on time, against 82.5% for the 5am–8am slot. By evening the aircraft flying these rotations have absorbed a full day of small delays and there is no slack left to recover in. The 5am–8am window is the busiest, with 650 flights scheduled in it.
Explore
Filter ATL to SEA by airline, time, month and day
Pick a breakdown and a carrier. The dashed mark on each row is the same slice for every US flight.
On ATL to SEA, the best departure window is 5am–8am at 82.5% on time and the worst is 5pm–8pm at 63.8%, a wide gap of 18.7 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am82.5%
- 8–11am81.2%
- 11am–2pm80.9%
- 2–5pm72.6%
- 5–8pm63.8%
- 8pm–5am75.7%
best all US flightsScale 55% to 95%.
Across the year
When delays peak on this route
This route's year swings by 28 points from best month to worst, which is wide. An annual average tells you very little about the week you are actually flying, so read the strip rather than the headline if your dates are fixed.
December is the weak month at 61.1% on time, against 89.0% in September. Winter delays cluster: a single storm system can account for most of a month's shortfall, so an average December hides both very good weeks and genuinely unflyable days. July was the busiest month here, with 348 flights.
Across the week, Saturday is the strongest day at 82.2% on time and Friday the weakest at 72.9%, a spread of 9 points.
Delay causes
Why this route gets delayed
Carrier accounts for 52% of the 43,000 delay minutes carriers reported here, and the remaining four split what is left.
- 52%Carrier
- 27%National Airspace System
- 18%Late-arriving aircraft
- 3%Extreme weather
- 0%Security
The largest share of delay minutes, 52%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 22,000 of the 43,000 delay minutes reported here. The split is drawn from 43,306 reported delay minutes.
Cancellations are rare at 0.73%, 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 stage length
What a delay here actually costs
5.8% 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 about an hour, which a normal layover absorbs.
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 return leg is a different operation and performs like one: it runs 84.0% on time across 3,294 flights, 7 points above this direction. Departure banks, aircraft rotations and the congestion at each end all differ, so scoring the two directions together would average away a real 7 points of difference.
The sample behind these figures is 3,297 flights, enough that the headline rate is stable to within roughly a point. The hour-block and month splits divide that further, so read the thinner bars with more caution than the headline.
Work out the risk of missing a connection in SEA after this flight
What to do with this
Booking this route
Put together: the calendar is the biggest lever here, not the carrier or the hour. September runs 89.0% on time and December 61.1%, a swing of 28 points. If the dates move at all, move them out of December before you think about anything else. 3,265 completed flights over 12 months sit behind that.
Common questions
ATL to SEA questions
How often is ATL to SEA delayed?
About one flight in four arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 23.3% of the 3,297 flights in this analysis, against 22.7% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on ATL to SEA?
Delta Air Lines leads at 76.8% on time across 2,404 flights. Alaska Airlines is at the other end on 76.4%, a gap of half a point. Sample size matters as much as the percentage: a rate built from a few hundred flights moves around far more than one built from ten thousand.
What time of day has the fewest delays on ATL to SEA?
The 5am–8am departure window is the strongest at 82.5% on time. The 5pm–8pm window is the weakest at 63.8%, 19 points behind. Later departures inherit delays from earlier flights the same aircraft has already flown, which is why the curve slopes the way it does.
How bad are December delays on ATL to SEA?
December is the weakest month at 61.1% on time, compared with 89.0% in September. Across the year that is 28 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.
Related
Where to go next
- SEA to ATL — the return legseparate record
- Hartsfield-Jackson Atlanta International (ATL) delay statistics
- Seattle-Tacoma International (SEA) delay statistics
- Delta Air Lines on ATL to SEA76.8%
- Alaska Airlines on ATL to SEA76.4%
- ATL to LGA, a related route72.3%
- LAX to SEA, a related route85.0%
- ATL to MCO, a related route70.3%
- Delta Air Lines on-time record76.8%
- Alaska Airlines on-time record76.4%
- The best time of day to fly, according to 7.05 million flight records
- Worst months to fly in the US, ranked by the data
Direction matters. ATL to SEA and SEA to ATL are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
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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.