Carrier route record

DLIAD→ATL

Delta Air Lines · Washington to Atlanta

Flights: 2,219
Period: July 2025 to June 2026
Share of route: 56%
Carriers: 4

Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Delta Air Lines.

Delta on IAD to ATL lands a B, 3 points better than the national rate of 77.6%. About one flight in five arrives 15 minutes late or worse, and those flights are late by an hour and a half on average. That is a workable record, not a spotless one. That rests on 2,219 flights. The strongest carrier on the route with a full sample, United Airlines, flew 1,097 at 80.9% on time.

The US average over the same twelve months is 77.6%, so there is little to separate Delta on IAD to ATL from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.

On time

81.0%

Arrivals under 15 minutes late, of 2,146 completed flights

Avg delay

89 min

Across delayed arrivals only, not all flights

Cancelled

2.79%

National rate is 1.81%

Whole route

79.2%

Every carrier on IAD to ATL, 3,976 flights

These figures cover 2,219 flights between July 2025 and June 2026. The median arrival is 12 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

Delta against every carrier on IAD to ATL

Delta flew 2,219 of the 3,976 flights on IAD to ATL, most of the route. Its 81.0% on time is 2 points better than the route as a whole, which runs 79.2%. Ranked by on-time rate it is first of four carriers on the route, where the range runs from Delta at 81.0% to Frontier at 69.9%. One of those carriers flew fewer than 365 flights here, so treat their positions as rough.

The choice of carrier is not cosmetic here. United Airlines arrives on time 80.9% of the time; Frontier Airlines manages 69.9%. Sample sizes sit next to every figure, because a two-point gap across 639 flights means less than a ten-point one.

On-time performance by carrier on IAD to ATL
Airline	Flights	On time	Avg delay	Cancelled	Grade
Delta Air Lines (this page)	2,219	81.0%	89 min	2.79%	B
United Airlines	1,097	80.9%	89 min	0.46%	B+
Republic Airwaysthin sample	21	80.0%	41 min	4.76%	B−
Frontier Airlines	639	69.9%	85 min	2.19%	C

United leads Frontier by 11 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.

Flight by flight

Delta flight numbers on IAD to ATL

DL 135406:0081.4% · 300 flights

Departure window

When Delta runs best on this route

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 13 points, against 11 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am613 flights85.7%
8am–11am367 flights85.1%
11am–2pm395 flights81.4%
2pm–5pm345 flights80.1%
5pm–8pm499 flights72.6%
8pm–5am—

Scale runs 65% to 90%. Rows with fewer than 30 flights show a dash.

Book the early departure. Flights leaving between 5am–8am arrive on time 85.7% of the time, against 72.6% 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 5am–8am window is the busiest, with 613 flights scheduled in it.

Across the year

Delta on IAD to ATL through the year

Darker means more delays. Figures are on-time percentages.April best, July worst

July is the worst month at 68.1% on time, 23 points below April, the best at 91.0%. 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 207 flights.

Across the week, Thursday is the strongest day at 85.5% on time and Sunday the weakest at 75.3%. 10 points is a smaller lever than departure hour, but it is free.

Delay causes

Why Delta runs late on this route

One category carries most of the weight here. Carrier accounts for 43% of the 36,000 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.

Carrier
43%
Late-arriving aircraft
39%
National Airspace System
16%
Extreme weather
3%

39% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. That is a cascade, and cascades start small and grow through the day. Across 36,000 reported delay minutes here, that single category outweighs weather by 15 to one. It is the strongest argument for booking the first departure of the morning, when the aircraft has been sitting at the gate overnight with nothing to inherit. The split is drawn from 36,085 reported delay minutes.

The largest share of delay minutes, 43%, 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 15,000 of the 36,000 delay minutes reported here.

Cancellations run at 2.79%, against 1.81% nationally. That is roughly one flight in 40 cancelled outright. A cancelled flight is invisible in every on-time figure on this page, so the punctuality numbers above describe only the flights that actually operated.

Connections and stage length

What a delay here costs

7.5% of arrivals land an hour or more late, close to the national 8.1%. That is the figure that decides a connection, and it says a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last an hour and a half, which a normal layover absorbs.

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. It is also long enough that the aircraft usually flies three or four legs a day rather than six, which slows how fast delay compounds.

The return leg is a different operation and performs like one: it runs 77.8% on time across 2,219 flights, 3 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 3 points of difference.

The sample behind these figures is 2,219 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 Delta on IAD to ATL

Put together: the calendar is the biggest lever here, not the carrier or the hour. April runs 91.0% on time and July 68.1%, a swing of 23 points. If the dates move at all, move them out of July before you think about anything else. 2,146 completed flights over 12 months sit behind that.

Where to go next

Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.

Key figures