Route reliability record
ATL→IAD
Atlanta to Washington
- Flights
- 4,005
- Period
- September 2025 to August 2026
- Distance
- 534 mi
- Carriers
- 4
This route lands a B, about a point worse than the national rate of 77.3%. About one flight in four arrives 15 minutes late or worse, and those flights are late by a little over an hour on average. That rests on 4,005 ATL to IAD flights, of which United Airlines flew 1,091 at 81.6% on time.
Best time to fly ATL to IAD: a 5am–8am departure, ideally on a Thursday. Flights in that window arrived on time 89.8% of the time and Thursday flights 81.4%, against 76.4% for the route overall.
United Airlines is the most reliable of the three carriers covered here at 81.6% on time across 1,091 flights.
Key figures
On time
76.4%
Arrivals under 15 minutes late, of 3,915 completed flights
Avg delay
79 min
Across delayed arrivals only, not all flights
Cancelled
2.12%
National rate is 1.89%
Best carrier
United
81.6% on time across 1,091 flights
These figures cover 4,005 flights between September 2025 and August 2026. Beyond the headline rate, 9.9% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Carrier by carrier
Which airline is most reliable on ATL to IAD
The choice of carrier is not cosmetic here. United Airlines arrives on time 81.6% of the time; Frontier Airlines manages 63.1%. Sample sizes sit next to every figure, because a two-point gap across 661 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 1,091 | 81.6% | 78 min | 0.92% | B+ |
| Republic Airwaysthin sample | 20 | 80.0% | 325 min | 0.00% | B+ |
| Delta Air Lines | 2,233 | 77.8% | 76 min | 2.73% | B |
| Frontier Airlines | 661 | 63.1% | 82 min | 2.12% | D |
The spread between United and Frontier is 18 points, wide enough that it should decide the booking. On a hundred trips that is 18 more arrivals inside the on-time window.
Flight by flight
Flights on ATL to IAD
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 Washington
Every airline on this route and on the routes between nearby airports, ranked by how often a scheduled flight actually operated and arrived on time. 3 of the top 5 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. ATL → IADAtlanta to Washington | United Airlines | 80.8% | 81.6% | 0.92% | 5am–8am, Sat | UA 632 09:35 |
| 2. ATL → BWIAtlanta to Baltimore | Delta Air Lines | 77.1% | 78.7% | 2.04% | 8am–11am, Wed | DL 801 08:55 |
| 3. ATL → IADAtlanta to Washington | Delta Air Lines | 75.7% | 77.8% | 2.73% | 5am–8am, Thu | DL 1444 10:00 |
| 4. ATL → BWIAtlanta to Baltimore | Southwest Airlines | 75.5% | 77.0% | 1.93% | 5am–8am, Wed | — |
| 5. ATL → DCAAtlanta to Washington | Southwest Airlines | 69.2% | 70.4% | 1.67% | 5am–8am, Tue | — |
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 24 points, against 18 points between the best and worst carrier.
- 5am–8am394 flights89.8%
- 8am–11am814 flights84.4%
- 11am–2pm387 flights83.0%
- 2pm–5pm981 flights72.2%
- 5pm–8pm748 flights72.6%
- 8pm–5am681 flights65.5%
Scale runs 55% to 95%.
Book the early departure. Flights leaving between 5am–8am arrive on time 89.8% of the time, against 65.5% for the overnight window. That is 24 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 2pm–5pm window is the busiest, with 981 flights scheduled in it.
Explore
Filter ATL to IAD 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 IAD, the best departure window is 5am–8am at 89.8% on time and the worst is 8pm–5am at 65.5%, a wide gap of 24.3 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am89.8%
- 8–11am84.4%
- 11am–2pm83.0%
- 2–5pm72.2%
- 5–8pm72.6%
- 8pm–5am65.5%
best all US flightsScale 55% to 95%.
Across the year
When delays peak on this route
This route's year swings by 18 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 66.6% on time, 18 points below April, the best at 84.6%. 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. May was the busiest month here, with 406 flights.
Across the week, Thursday is the strongest day at 81.4% on time and Sunday the weakest at 71.2%, a spread of 10 points.
Delay causes
Why this route gets delayed
Carrier accounts for 43% of the 73,000 delay minutes carriers reported here, and the remaining four split what is left.
- 43%Carrier
- 33%Late-arriving aircraft
- 19%National Airspace System
- 5%Extreme weather
The largest share of delay minutes, 43%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 31,000 of the 73,000 delay minutes reported here. The split is drawn from 72,946 reported delay minutes.
The practical consequence: the 5am–8am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 89.8% on time here.
Cancellations sit at 2.12% against a national 1.89%, which is ordinary. Diversions add another 0.12%.
Connections and stage length
What a delay here actually costs
9.9% of arrivals land a full hour or more behind schedule, against 8.3% nationally. Ninety minutes is the honest minimum for a connection here, and two hours if the onward flight is on a separate ticket.
The 534 miles between these two airports put this in the middle of the US network, around two and a half to three hours of block time. That is enough cruise to absorb a ten-minute late pushback and not enough to absorb thirty.
The return leg runs 78.0% on time across 4,003 flights, within 2 points of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.
The sample behind these figures is 4,005 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 IAD 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. April runs 84.6% on time and July 66.6%, a swing of 18 points. If the dates move at all, move them out of July before you think about anything else. 3,915 completed flights over 12 months sit behind that.
Common questions
ATL to IAD questions
How often is ATL to IAD 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 23.6% of the 4,005 flights in this analysis, against 22.7% nationally. Delayed flights are late by a little over an hour on average.
Which airline is most reliable on ATL to IAD?
United Airlines leads at 81.6% on time across 1,091 flights. Frontier Airlines is at the other end on 63.1%, a gap of 18 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 ATL to IAD?
The 5am–8am departure window is the strongest at 89.8% on time. The 8pm–5am window is the weakest at 65.5%, 24 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 ATL to IAD?
July is the weakest month at 66.6% on time, compared with 84.6% in April. Across the year that is 18 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
- IAD to ATL — the return legseparate record
- Hartsfield-Jackson Atlanta International (ATL) delay statistics
- Washington Dulles International (IAD) delay statistics
- United Airlines on ATL to IAD81.6%
- Delta Air Lines on ATL to IAD77.8%
- Frontier Airlines on ATL to IAD63.1%
- ATL to LGA, a related route72.3%
- DEN to IAD, a related route81.8%
- ATL to MCO, a related route70.3%
- United Airlines on-time record81.6%
- Republic Airways on-time record80.0%
- Delta Air Lines on-time record77.8%
- Why the first flight of the morning is statistically safest
- Same route, different airline: where the carrier you pick matters most
Direction matters. ATL to IAD and IAD 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.