Route reliability record

ATL→BOS

Atlanta to Boston

Flights: 4,904
Period: June 2025 to May 2026
Distance: 946 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 4,904 flights, of which Delta Air Lines flew 3,658 at 75.2% on time.

The US average over the same twelve months is 77.4%, so there is little to separate this route from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.

On time

73.6%

Arrivals under 15 minutes late, of 4,804 completed flights

Avg delay

64 min

Across delayed arrivals only, not all flights

Cancelled

1.96%

National rate is 1.80%

Best carrier

Delta

75.2% on time across 3,658 flights

These figures cover 4,904 flights between June 2025 and May 2026. Beyond the headline rate, 9.3% 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 BOS

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.

On-time performance by carrier on ATL to BOS
Airline	Flights	On time	Avg delay	Cancelled	Grade
Delta Air Lines	3,658	75.2%	60 min	1.80%	B
JetBlue Airways	846	70.8%	85 min	2.72%	C
Frontier Airlinesthin sample	350	64.7%	57 min	2.00%	D
Spirit Airlinesthin sample	50	60.0%	74 min	0.00%	D+

No carrier stands out. Delta tops the table at 75.2%, 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 24 points, against 4 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am734 flights86.7%
8am–11am804 flights86.6%
11am–2pm950 flights74.9%
2pm–5pm889 flights62.4%
5pm–8pm538 flights63.8%
8pm–5am989 flights67.4%

Scale runs 55% to 90%. Rows with fewer than 30 flights show a dash.

Book the early departure. Flights leaving between 5am–8am arrive on time 86.7% of the time, against 62.4% for the afternoon 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.

Across the year

When delays peak on this route

This route's year swings by 17 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.August best, July worst

July is the worst month at 64.9% on time, 17 points below August, the best at 82.3%. 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.

Across the week, Saturday is the strongest day at 79.6% on time and Sunday the weakest at 67.1%. 13 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 82,000 reported delay minutes.

National Airspace System
36%
Carrier
36%
Late-arriving aircraft
24%
Extreme weather
4%
Security
0%

The largest share of delay minutes, 36%, 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 29,000 of the 82,000 delay minutes reported here.

36% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 30,000 minutes out of 82,000, against a national NAS share of 21%.

Cancellations sit at 1.96% against a national 1.80%, which is ordinary. Diversions add another 0.08%.

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. 9.3% 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 946 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 77.9% on time across 4,903 flights, 4 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 4 points of difference.

The sample behind these figures is 4,904 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. August runs 82.3% on time and July 64.9%, a swing of 17 points. If the dates move at all, move them out of July before you think about anything else.

Common questions

ATL to BOS questions

How often is ATL to BOS 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 4,904 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 BOS?

Delta Air Lines leads at 75.2% on time across 3,658 flights. JetBlue Airways is at the other end on 70.8%, 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 ATL to BOS?

The 5am–8am departure window is the strongest at 86.7% on time. The 2pm–5pm window is the weakest at 62.4%, 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 BOS?

July is the weakest month at 64.9% on time, compared with 82.3% in August. Across the year that is 17 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 BOS and BOS 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