Boston, MA · departure reliability
BOS
Boston Logan International
- Departures
- 143,082
- Period
- July 2025 to June 2026
- Carriers
- 11
- US rank
- #12 by volume
Boston
Boston Logan International sits in the middle of the pack with a B. Close to three flights in four arrive on time by the DOT's definition, 2 points worse than the national rate of 77.6%. The late ones land a little over an hour behind schedule. That rests on 143,082 flights, of which Allegiant Air flew 633 at 84.9% on time.
Allegiant Air is the most reliable of the eleven carriers covered here at 84.9% on time across 633 flights.
Key figures
On time
75.6%
Departures arriving under 15 minutes late at their destination
Avg delay
72 min
Across delayed flights only
Cancelled
2.64%
National rate is 1.81%
Best carrier
Allegiant
84.9% on time here
These figures cover 143,000 flights between July 2025 and June 2026. Beyond the headline rate, 9.5% 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 airlines run best out of BOS
The choice of carrier is not cosmetic here. Allegiant Air arrives on time 84.9% of the time; Spirit Airlines manages 65.3%. Sample sizes sit next to every figure, because a two-point gap across 2,325 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| JetBlue Airways | 37,487 | 72.0% | 70 min | 2.51% | C |
| Republic Airways | 33,650 | 78.1% | 67 min | 3.88% | B− |
| Delta Air Lines | 26,419 | 76.8% | 73 min | 2.03% | B |
| American Airlines | 16,933 | 78.3% | 91 min | 2.56% | B |
| United Airlines | 12,917 | 78.6% | 76 min | 1.90% | B |
| Southwest Airlines | 7,197 | 71.3% | 63 min | 1.53% | C |
| Alaska Airlines | 2,486 | 71.2% | 53 min | 1.17% | C |
| Spirit Airlines | 2,325 | 65.3% | 79 min | 4.82% | C− |
| Envoy Air | 2,013 | 79.9% | 74 min | 2.24% | B |
| Frontier Airlines | 931 | 70.3% | 60 min | 1.83% | C |
| Allegiant Air | 633 | 84.9% | 86 min | 0.47% | B+ |
Spirit Airlines cancels 4.8% 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.
Route by route
Busiest routes out of BOS
Route-level records vary far more than the airport average. These are the 25 busiest departures from BOS, each with its own on-time rate against the airport-wide 75.6%.
| Route | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| BOS to DCA · Washington | 9,082 | 74.0% | 72 min | 3.88% | C− |
| BOS to ORD · Chicago | 7,637 | 72.7% | 84 min | 2.91% | C |
| BOS to LGA · New York | 7,251 | 77.7% | 77 min | 5.70% | B− |
| BOS to JFK · New York | 5,738 | 75.5% | 73 min | 4.55% | B− |
| BOS to PHL · Philadelphia | 4,961 | 76.5% | 87 min | 2.92% | B |
| BOS to ATL · Atlanta | 4,931 | 78.5% | 69 min | 1.99% | B |
| BOS to LAX · Los Angeles | 4,713 | 74.9% | 76 min | 1.42% | C |
| BOS to SFO · San Francisco | 4,676 | 72.6% | 65 min | 1.22% | C |
| BOS to MCO · Orlando | 4,606 | 70.1% | 77 min | 2.74% | C |
| BOS to CLT · Charlotte | 4,017 | 82.6% | 82 min | 2.69% | B |
| BOS to EWR · Newark | 3,906 | 74.9% | 79 min | 4.33% | C− |
| BOS to DEN · Denver | 3,899 | 76.5% | 58 min | 1.18% | B |
| BOS to DFW · Dallas-Fort Worth | 3,740 | 76.1% | 84 min | 3.16% | B− |
| BOS to BWI · Baltimore | 3,551 | 78.9% | 73 min | 2.70% | B |
| BOS to MIA · Miami | 3,417 | 77.7% | 75 min | 2.25% | B |
| BOS to FLL · Fort Lauderdale | 3,417 | 66.7% | 73 min | 3.45% | C− |
| BOS to BNA · Nashville | 2,945 | 70.4% | 68 min | 1.87% | C |
| BOS to TPA · Tampa | 2,822 | 74.8% | 71 min | 2.48% | C |
| BOS to RDU · Raleigh | 2,816 | 76.3% | 76 min | 2.41% | B |
| BOS to DTW · Detroit | 2,591 | 77.6% | 75 min | 2.12% | B |
| BOS to SEA · Seattle | 2,461 | 71.4% | 54 min | 1.26% | C |
| BOS to RSW · Fort Myers | 2,253 | 70.5% | 66 min | 2.62% | C |
| BOS to PBI · West Palm Beach | 2,183 | 65.7% | 72 min | 3.02% | C− |
| BOS to PIT · Pittsburgh | 2,152 | 78.7% | 69 min | 2.65% | B |
| BOS to IAH · Houston | 2,027 | 81.8% | 67 min | 1.43% | B |
Departure window
The best time of day to leave BOS
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 28 points, against 20 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am28,538 flights88.2%
- 8am–11am29,993 flights84.1%
- 11am–2pm22,204 flights78.3%
- 2pm–5pm25,500 flights69.2%
- 5pm–8pm25,300 flights62.3%
- 8pm–5am11,547 flights59.9%
Scale runs 50% to 95%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is where this operation falls apart: 59.9% on time, against 88.2% 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 8am–11am window is the busiest, with 29,993 flights scheduled in it.
Across the year
When BOS runs late
BOS's year swings by 13 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.
December is the weak month at 68.7% on time, against 81.4% in August. Winter delays cluster: a single storm system can account for most of a month's shortfall, so an average December hides both very good weeks and genuinely unflyable days. July was the busiest month here, with 12,912 flights.
Across the week, Wednesday is the strongest day at 79.8% on time and Sunday the weakest at 70.4%. 9 points is a smaller lever than departure hour, but it is free.
Delay causes
Why BOS gets delayed
One category carries most of the weight here. Late-arriving aircraft accounts for 42% of the 2.43 million 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.
- 42%Late-arriving aircraft
- 28%Carrier
- 27%National Airspace System
- 3%Extreme weather
- 0%Security
42% 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 2.43 million reported delay minutes here, that single category outweighs weather by 16 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 2,429,428 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 88.2% on time here.
Cancellations run at 2.64%, against 1.81% nationally. That is about one flight in 40 cancelled outright. A cancelled flight is invisible in every on-time figure on this page, so the punctuality numbers above describe only the flights that actually operated.
For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 9.5% 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.
143,082 flights sit behind these numbers, which is a large enough sample that the headline rate is not moving on noise. Where a sub-group falls below 30 flights the site shows a dash instead of a percentage.
What to do with this
Flying out of BOS
Put together: the calendar is the biggest lever here, not the carrier or the hour. August runs 81.4% on time and December 68.7%, a swing of 13 points. If the dates move at all, move them out of December before you think about anything else. 138,920 completed flights over 12 months sit behind that.
Common questions
BOS delay questions
How often is Boston (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 24.4% of the 143,082 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 Boston (BOS)?
Allegiant Air leads at 84.9% on time across 633 flights. Spirit Airlines is at the other end on 65.3%, 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 Boston (BOS)?
The 5am–8am departure window is the strongest at 88.2% on time. The 8pm–5am window is the weakest at 59.9%, 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 December delays on Boston (BOS)?
December is the weakest month at 68.7% on time, compared with 81.4% in August. Across the year that is 13 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.
Related
Where to go next
- BOS to DCA — Washington74.0%
- BOS to ORD — Chicago72.7%
- BOS to LGA — New York77.7%
- BOS to JFK — New York75.5%
- BOS to PHL — Philadelphia76.5%
- BOS to ATL — Atlanta78.5%
- JetBlue Airways on-time record72.0%
- Republic Airways on-time record78.1%
- Delta Air Lines on-time record76.8%
- American Airlines on-time record78.3%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Updated monthly. How this data is collected.