Route reliability record

BNA→BOS

Nashville to Boston

Flights: 2,946
Period: July 2025 to June 2026
Distance: 942 mi
Carriers: 6

This route sits in the middle of the pack with a C. About seven flights in ten arrive on time by the DOT's definition, 9 points worse than the national rate of 77.6%. The late ones land a little over an hour behind schedule. That rests on 2,946 flights, of which Republic Airways flew 500 at 80.9% on time.

Republic Airways is the most reliable of the four carriers covered here at 80.9% on time across 500 flights.

On time

69.0%

Arrivals under 15 minutes late, of 2,884 completed flights

Avg delay

71 min

Across delayed arrivals only, not all flights

Cancelled

1.97%

National rate is 1.81%

Best carrier

Republic

80.9% on time across 500 flights

These figures cover 2,946 flights between July 2025 and June 2026. Beyond the headline rate, 11.8% 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 BNA to BOS

The choice of carrier is not cosmetic here. Republic Airways arrives on time 80.9% of the time; Southwest Airlines manages 60.6%. Sample sizes sit next to every figure, because a two-point gap across 997 flights means less than a ten-point one.

On-time performance by carrier on BNA to BOS
Airline	Flights	On time	Avg delay	Cancelled	Grade
American Airlinesthin sample	2	100.0%	—	0.00%	A+
Republic Airways	500	80.9%	90 min	3.60%	B−
Delta Air Lines	533	71.5%	105 min	0.75%	C+
JetBlue Airways	874	70.5%	70 min	2.29%	C
Spirit Airlinesthin sample	40	65.8%	125 min	5.00%	C−
Southwest Airlines	997	60.6%	53 min	1.40%	D

Republic Airways cancels 3.6% 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 38 points, against 20 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am536 flights89.1%
8am–11am537 flights77.4%
11am–2pm660 flights66.6%
2pm–5pm285 flights50.7%
5pm–8pm710 flights61.4%
8pm–5am218 flights54.2%

Scale runs 40% to 95%. Rows with fewer than 30 flights show a dash.

Book the early departure. Flights leaving between 5am–8am arrive on time 89.1% of the time, against 50.7% for the afternoon window. That is 38 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 5pm–8pm window is the busiest, with 710 flights scheduled in it.

Across the year

When delays peak on this route

This route's year swings by 23 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, September worst

Delays peak in September, when the on-time rate falls to 55.5%. August is the strongest month at 78.9%. Moving a flexible trip across that boundary buys 23 points. October was the busiest month here, with 330 flights.

Across the week, Saturday is the strongest day at 81.8% on time and Thursday the weakest at 61.2%. 21 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 64,000 reported delay minutes.

Late-arriving aircraft
38%
National Airspace System
30%
Carrier
30%
Extreme weather
3%

38% 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 64,000 reported delay minutes here, that single category outweighs weather by 14 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 63,663 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 89.1% on time here.

Cancellations sit at 1.97% against a national 1.81%, which is ordinary. Diversions add another 0.14%.

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. 11.8% 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 942 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 70.4% on time across 2,945 flights, within about 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 2,946 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 78.9% on time and September 55.5%, a swing of 23 points. If the dates move at all, move them out of September before you think about anything else. 2,884 completed flights over 12 months sit behind that.

Common questions

BNA to BOS questions

How often is BNA to BOS delayed?

About one flight in three arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 31.0% of the 2,946 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 BNA to BOS?

Republic Airways leads at 80.9% on time across 500 flights. Southwest Airlines is at the other end on 60.6%, a gap of 20 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 BNA to BOS?

The 5am–8am departure window is the strongest at 89.1% on time. The 2pm–5pm window is the weakest at 50.7%, 38 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 September delays on BNA to BOS?

September is the weakest month at 55.5% on time, compared with 78.9% in August. Across the year that is 23 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. BNA to BOS and BOS to BNA 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