Route reliability record

ATL→BWI

Atlanta to Baltimore

Flights: 5,430
Period: June 2025 to May 2026
Distance: 577 mi
Carriers: 4

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 77.4%. The late ones land about an hour behind schedule. That rests on 5,430 flights, of which Southwest Airlines flew 1,577 at 78.2% on time.

Southwest Airlines is the most reliable of the three carriers covered here at 78.2% on time across 1,577 flights.

On time

73.9%

Arrivals under 15 minutes late, of 5,297 completed flights

Avg delay

66 min

Across delayed arrivals only, not all flights

Cancelled

2.23%

National rate is 1.80%

Best carrier

Southwest

78.2% on time across 1,577 flights

These figures cover 5,430 flights between June 2025 and May 2026. Beyond the headline rate, 9.6% 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 ATL to BWI

The choice of carrier is not cosmetic here. Southwest Airlines arrives on time 78.2% of the time; Frontier Airlines manages 59.4%. Sample sizes sit next to every figure, because a two-point gap across 848 flights means less than a ten-point one.

On-time performance by carrier on ATL to BWI
Airline	Flights	On time	Avg delay	Cancelled	Grade
Southwest Airlines	1,577	78.2%	67 min	2.47%	B
Spirit Airlinesthin sample	167	77.4%	65 min	1.20%	B
Delta Air Lines	2,838	75.7%	63 min	2.08%	B
Frontier Airlines	848	59.4%	72 min	2.48%	D

The spread between Southwest and Frontier is 19 points, wide enough that it should decide the booking. On a hundred trips that is 19 more arrivals inside the on-time window.

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 28 points, against 19 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am558 flights89.6%
8am–11am879 flights84.8%
11am–2pm812 flights83.9%
2pm–5pm1,219 flights71.5%
5pm–8pm918 flights61.6%
8pm–5am1,044 flights62.2%

Scale runs 55% to 95%. Rows with fewer than 30 flights show a dash.

The 5pm–8pm window is where this operation falls apart: 61.6% on time, against 89.6% 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.

Across the year

When delays peak on this route

This route's year swings by 33 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, June worst

June is the worst month at 54.9% on time, 33 points below September, the best at 88.1%. 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.

Across the week, Wednesday is the strongest day at 81.7% on time and Sunday the weakest at 66.9%. 15 points is a smaller lever than departure hour, but it is free.

Delay causes

Why this route gets delayed

Carriers report a reason for every delay minute they cause, in five DOT categories. The split below is by minutes, not by number of flights, so a handful of very long weather delays weighs as much as many short ones. It covers 91,000 reported delay minutes.

Carrier
40%
Late-arriving aircraft
35%
National Airspace System
20%
Extreme weather
5%
Security
0%

35% 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 91,000 reported delay minutes here, that single category outweighs weather by 7 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 largest share of delay minutes, 40%, 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 36,000 of the 91,000 delay minutes reported here.

Cancellations sit at 2.23% against a national 1.80%, which is ordinary. Diversions add another 0.22%.

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. 9.6% of arrivals land a full hour or more behind schedule, against 8.2% 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 577 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 79.4% on time across 5,431 flights, 6 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 6 points of difference.

The sample behind these figures is 5,430 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 88.1% on time and June 54.9%, a swing of 33 points. If the dates move at all, move them out of June before you think about anything else.

Common questions

ATL to BWI questions

How often is ATL to BWI 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 26.1% of the 5,430 flights in this analysis, against 22.6% nationally. Delayed flights are late by about an hour on average.

Which airline is most reliable on ATL to BWI?

Southwest Airlines leads at 78.2% on time across 1,577 flights. Frontier Airlines is at the other end on 59.4%, a gap of 19 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 BWI?

The 5am–8am departure window is the strongest at 89.6% on time. The 5pm–8pm window is the weakest at 61.6%, 28 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 June delays on ATL to BWI?

June is the weakest month at 54.9% on time, compared with 88.1% in September. Across the year that is 33 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. ATL to BWI and BWI to ATL 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, June 2025 to May 2026. Updated monthly. How this data is collected.

Key figures