Route reliability record

DCA→STL

Washington to St. Louis

Flights: 2,414
Period: July 2025 to June 2026
Distance: 719 mi
Carriers: 5

This route sits in the middle of the pack with a C. Close to three flights in four arrive on time by the DOT's definition, 4 points worse than the national rate of 77.6%. The late ones land a little over an hour behind schedule. That rests on 2,414 flights, of which Southwest Airlines flew 1,403 at 75.7% on time.

The national on-time rate over the same period is 77.6%, so this route runs 4 points behind the country as a whole. Across a thousand flights that is about 40 extra late arrivals.

On time

73.6%

Arrivals under 15 minutes late, of 2,352 completed flights

Avg delay

73 min

Across delayed arrivals only, not all flights

Cancelled

2.40%

National rate is 1.81%

Best carrier

Southwest

75.7% on time across 1,403 flights

These figures cover 2,414 flights between July 2025 and June 2026. Beyond the headline rate, 9.8% of arrivals land a full hour or more behind schedule. That is the number that wrecks a connection, and it is not visible in an on-time percentage alone.

Carrier by carrier

Which airline is most reliable on DCA to STL

The choice of carrier is not cosmetic here. Southwest Airlines arrives on time 75.7% of the time; PSA Airlines manages 67.4%. Sample sizes sit next to every figure, because a two-point gap across 615 flights means less than a ten-point one.

On-time performance by carrier on DCA to STL
Airline	Flights	On time	Avg delay	Cancelled	Grade
Envoy Airthin sample	21	90.5%	39 min	0.00%	A+
Republic Airwaysthin sample	200	79.8%	61 min	3.50%	B−
Southwest Airlines	1,403	75.7%	66 min	1.21%	B
American Airlinesthin sample	175	68.4%	95 min	2.29%	C
PSA Airlines	615	67.4%	82 min	4.88%	C−

PSA Airlines cancels 4.9% of what it schedules here, the highest in the table. A cancelled flight never appears in an on-time rate, so read that column alongside the punctuality one rather than after it.

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 26 points, against 8 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am107 flights86.1%
8am–11am509 flights83.9%
11am–2pm534 flights80.6%
2pm–5pm574 flights68.7%
5pm–8pm403 flights60.2%
8pm–5am287 flights65.8%

Scale runs 50% to 90%. Rows with fewer than 30 flights show a dash.

The 5pm–8pm window is where this operation falls apart: 60.2% on time, against 86.1% 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 2pm–5pm window is the busiest, with 574 flights scheduled in it.

Across the year

When delays peak on this route

This route's year swings by 21 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.

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

July is the worst month at 60.6% on time, 21 points below September, the best at 81.3%. 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. October was the busiest month here, with 223 flights.

Across the week, Saturday is the strongest day at 79.4% on time and Sunday the weakest at 65.7%. 14 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. Late-arriving aircraft accounts for 51% of the 45,000 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.

Late-arriving aircraft
51%
Carrier
30%
National Airspace System
12%
Extreme weather
6%
Security
1%

51% 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 45,000 reported delay minutes here, that single category outweighs weather by 9 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 45,204 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 86.1% on time here.

Cancellations sit at 2.40% against a national 1.81%, which is ordinary. Diversions add another 0.17%.

Connections and stage length

What a delay here actually costs

For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 9.8% of arrivals land a full hour or more behind schedule, against 8.1% nationally. A 45-minute layover does not survive that, and no amount of walking quickly changes it. Ninety minutes is the honest minimum here, and two hours if the onward flight is on a separate ticket.

The 719 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 runs 72.9% on time across 2,414 flights, within half a point 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 2,414 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. September runs 81.3% on time and July 60.6%, a swing of 21 points. If the dates move at all, move them out of July before you think about anything else. 2,352 completed flights over 12 months sit behind that.

Common questions

DCA to STL questions

How often is DCA to STL delayed?

About one flight in four arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 26.4% of the 2,414 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 DCA to STL?

Southwest Airlines leads at 75.7% on time across 1,403 flights. PSA Airlines is at the other end on 67.4%, a gap of 8 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 DCA to STL?

The 5am–8am departure window is the strongest at 86.1% on time. The 5pm–8pm window is the weakest at 60.2%, 26 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 DCA to STL?

July is the weakest month at 60.6% on time, compared with 81.3% in September. Across the year that is 21 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.

Where to go next

Direction matters. DCA to STL and STL to DCA 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.

Key figures