Route reliability record

ATL→BOS

Atlanta to Boston

Flights: 4,935
Period: July 2025 to June 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, 3 points worse than the national rate of 77.6%. The late ones land about an hour behind schedule. That rests on 4,935 flights, of which Delta Air Lines flew 3,666 at 76.2% on time.

Delta Air Lines is the most reliable of the three carriers covered here at 76.2% on time across 3,666 flights.

On time

74.5%

Arrivals under 15 minutes late, of 4,836 completed flights

Avg delay

63 min

Across delayed arrivals only, not all flights

Cancelled

1.95%

National rate is 1.81%

Best carrier

Delta

76.2% on time across 3,666 flights

These figures cover 4,935 flights between July 2025 and June 2026. Beyond the headline rate, 8.8% 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 ATL to BOS

The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 76.2% of the time; Frontier Airlines manages 66.4%. Sample sizes sit next to every figure, because a two-point gap across 400 flights means less than a ten-point one.

On-time performance by carrier on ATL to BOS
Airline	Flights	On time	Avg delay	Cancelled	Grade
Delta Air Lines	3,666	76.2%	59 min	1.72%	B
JetBlue Airways	848	71.2%	83 min	2.71%	C
Frontier Airlines	400	66.4%	57 min	2.50%	C
Spirit Airlinesthin sample	21	61.9%	57 min	0.00%	D+

Delta leads Frontier by 10 points. Real, but small enough that a better departure time on the weaker carrier can outweigh 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 23 points, against 10 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am759 flights86.6%
8am–11am804 flights86.7%
11am–2pm937 flights75.9%
2pm–5pm864 flights63.9%
5pm–8pm553 flights64.8%
8pm–5am1,018 flights68.5%

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

Book the morning departure. Flights leaving between 8am–11am arrive on time 86.7% of the time, against 63.9% for the afternoon window. That is 23 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 8pm–5am window is the busiest, with 1,018 flights scheduled in it.

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. June was the busiest month here, with 467 flights.

Across the week, Saturday is the strongest day at 81.5% on time and Sunday the weakest at 67.6%. 14 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 78,000 reported delay minutes.

National Airspace System
36%
Carrier
35%
Late-arriving aircraft
25%
Extreme weather
3%
Security
0%

The largest share of delay minutes, 35%, 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 28,000 of the 78,000 delay minutes reported here. The split is drawn from 78,325 reported delay minutes.

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 28,000 minutes out of 78,000, against a national NAS share of 21%.

Cancellations sit at 1.95% against a national 1.81%, which is ordinary. Diversions add another 0.06%.

Connections and stage length

What a delay here actually costs

8.8% 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 are the about an hour kind, which a normal layover absorbs.

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 78.5% on time across 4,931 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 4,935 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. 4,836 completed flights over 12 months sit behind that.

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 25.5% of the 4,935 flights in this analysis, against 22.4% 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 76.2% on time across 3,666 flights. Frontier Airlines is at the other end on 66.4%, a gap of 10 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 8am–11am departure window is the strongest at 86.7% on time. The 2pm–5pm window is the weakest at 63.9%, 23 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, July 2025 to June 2026. Updated monthly. How this data is collected.

Key figures