Route reliability record
SEA→ATL
Seattle to Atlanta
- Flights
- 3,276
- Period
- July 2025 to June 2026
- Distance
- 2,182 mi
- Carriers
- 2
This route lands a B+, 5 points better than the national rate of 77.6%. About one flight in six arrive 15 minutes late or worse, and those flights are late by a little over an hour on average. That is a workable record, not a spotless one. That rests on 3,276 flights, of which Delta Air Lines flew 2,371 at 83.8% on time.
Set against the rest of the country, this route's record is 5 points better than the US average of 77.6%. That gap is worth roughly 52 fewer late arrivals for every thousand flights.
Key figures
On time
82.8%
Arrivals under 15 minutes late, of 3,245 completed flights
Avg delay
73 min
Across delayed arrivals only, not all flights
Cancelled
0.55%
National rate is 1.81%
Best carrier
Delta
83.8% on time across 2,371 flights
These figures cover 3,276 flights between July 2025 and June 2026. The median arrival is 7 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.
Carrier by carrier
Which airline is most reliable on SEA to ATL
The two carriers here are closely matched: 4 points 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 | 2,371 | 83.8% | 86 min | 0.51% | B+ |
| Alaska Airlines | 905 | 80.3% | 46 min | 0.66% | B+ |
No carrier stands out. Delta tops the table at 83.8%, 4 points clear of the bottom, which is inside the range this kind of sample moves year to year.
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 13 points, against 4 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am647 flights89.9%
- 8am–11am492 flights83.2%
- 11am–2pm570 flights79.8%
- 2pm–5pm616 flights78.8%
- 5pm–8pm52 flights76.9%
- 8pm–5am899 flights82.5%
Scale runs 70% to 95%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 89.9% of the time, against 76.9% for the evening window. That is 13 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 8pm–5am window is the busiest, with 899 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 22 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.
July is the worst month at 69.3% on time, 22 points below February, the best at 91.1%. Summer afternoon convection and peak-season schedules land on the same weeks every year, so this is a pattern you can book around rather than a run of bad luck. July was the busiest month here, with 347 flights.
Across the week, Wednesday is the strongest day at 88.1% on time and Sunday the weakest at 79.4%. 9 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
One category carries most of the weight here. Carrier accounts for 57% of the 41,000 delay minutes carriers reported, and the remaining four split what is left. The split is by minutes rather than by flights, so a few very long delays count for as much as many short ones.
- 57%Carrier
- 22%Late-arriving aircraft
- 15%National Airspace System
- 5%Extreme weather
The largest share of delay minutes, 57%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. Unlike weather, that is a management outcome, and it is the category where the gap between two carriers on the same schedule is genuinely earned. It accounts for 23,000 of the 41,000 delay minutes reported here. The split is drawn from 40,854 reported delay minutes.
Cancellations are rare at 0.55%, below the national 1.81% 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
Badly late arrivals are rare here: only 4.6% land an hour or more behind schedule, against 8.1% 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 return leg is a different operation and performs like one: it runs 77.8% on time across 3,277 flights, 5 points below 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 5 points of difference.
The sample behind these figures is 3,276 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.
What to do with this
Booking this route
Put together: the calendar is the biggest lever here, not the carrier or the hour. February runs 91.1% on time and July 69.3%, a swing of 22 points. If the dates move at all, move them out of July before you think about anything else. 3,245 completed flights over 12 months sit behind that.
Common questions
SEA to ATL questions
How often is SEA to ATL delayed?
About one flight in six arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 17.2% of the 3,276 flights in this analysis, against 22.4% nationally. Delayed flights are late by a little over an hour on average.
Which airline is most reliable on SEA to ATL?
Delta Air Lines leads at 83.8% on time across 2,371 flights. Alaska Airlines is at the other end on 80.3%, a gap of 4 points. 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 SEA to ATL?
The 5am–8am departure window is the strongest at 89.9% on time. The 5pm–8pm window is the weakest at 76.9%, 13 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 July delays on SEA to ATL?
July is the weakest month at 69.3% on time, compared with 91.1% in February. Across the year that is 22 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
- ATL to SEA — the return legseparate record
- Seattle-Tacoma International (SEA) delay statistics
- Hartsfield-Jackson Atlanta International (ATL) delay statistics
- Delta Air Lines on-time record83.8%
- Alaska Airlines on-time record80.3%
- The best time of day to fly, according to 7.04 million flight records
- Worst months to fly in the US, ranked by the data
Direction matters. SEA to ATL and ATL to SEA are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Updated monthly. How this data is collected.