Carrier route record
AAMIA→BOS
American Airlines · Miami to Boston
- Flights
- 2,230
- Period
- July 2025 to June 2026
- Share of route
- 65%
- Carriers
- 6
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with American Airlines.
American on MIA to BOS sits in the middle of the pack with a C. About seven flights in ten arrive on time by the DOT's definition, 7 points worse than the national rate of 77.6%. The late ones land a little over an hour behind schedule. That rests on 2,230 flights, with a median arrival 3 minutes early.
The national on-time rate over the same period is 77.6%, so American on MIA to BOS runs 7 points behind the country as a whole. Across a thousand flights that is about 69 extra late arrivals.
Key figures
On time
70.7%
Arrivals under 15 minutes late, of 2,188 completed flights
Avg delay
71 min
Across delayed arrivals only, not all flights
Cancelled
1.75%
National rate is 1.81%
Whole route
69.7%
Every carrier on MIA to BOS, 3,415 flights
These figures cover 2,230 flights between July 2025 and June 2026. Beyond the headline rate, 11.4% 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
American against every carrier on MIA to BOS
American flew 2,230 of the 3,415 flights on MIA to BOS, most of the route. Its 70.7% on time is about level with the route as a whole at 69.7%. Ranked by on-time rate it is number three of six carriers on the route, where the range runs from Envoy at 100.0% to Spirit at 54.3%. Four of those carriers flew fewer than 365 flights here, so treat their positions as rough.
Only one carrier clears this site's 365-flight floor here, so there is no comparison to draw. The table below is the full picture.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Envoy Airthin sample | 1 | 100.0% | — | 0.00% | A+ |
| Republic Airwaysthin sample | 21 | 81.0% | 96 min | 0.00% | B+ |
| American Airlines (this page) | 2,230 | 70.7% | 71 min | 1.75% | C |
| Delta Air Lines | 888 | 70.0% | 78 min | 2.93% | C |
| JetBlue Airwaysthin sample | 89 | 66.7% | 68 min | 5.62% | C− |
| Spirit Airlinesthin sample | 186 | 54.3% | 70 min | 6.45% | F− |
Flight by flight
American flight numbers on MIA to BOS
Departure window
When American runs best on this route
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 33 points, against half a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am182 flights92.1%
- 8am–11am510 flights89.0%
- 11am–2pm265 flights61.8%
- 2pm–5pm193 flights73.3%
- 5pm–8pm499 flights59.2%
- 8pm–5am581 flights60.9%
Scale runs 50% to 100%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 59.2% on time, against 92.1% 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 8pm–5am window is the busiest, with 581 flights scheduled in it.
Across the year
American on MIA to BOS through the year
July is the worst month at 62.2% on time, 15 points below December, the best at 77.5%. 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. May was the busiest month here, with 212 flights.
Across the week, Saturday is the strongest day at 77.3% on time and Sunday the weakest at 65.1%. 12 points is a smaller lever than departure hour, but it is free.
Delay causes
Why American runs late on this route
One category carries most of the weight here. Late-arriving aircraft accounts for 44% of the 46,000 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.
- 44%Late-arriving aircraft
- 31%Carrier
- 21%National Airspace System
- 4%Extreme weather
- 0%Security
44% 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 46,000 reported delay minutes here, that single category outweighs weather by 10 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 45,581 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 92.1% on time here.
Cancellations sit at 1.75% against a national 1.81%, which is ordinary. Diversions add another 0.13%.
Connections and stage length
What a delay here costs
For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 11.4% 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 1,258 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 82.3% on time across 2,231 flights, 12 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 12 points of difference.
The sample behind these figures is 2,230 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 American on MIA to BOS
Put together: the calendar is the biggest lever here, not the carrier or the hour. December runs 77.5% on time and July 62.2%, a swing of 15 points. If the dates move at all, move them out of July before you think about anything else. 2,188 completed flights over 12 months sit behind that.
Related
Where to go next
- MIA to BOS, every carrier
- American on BOS to MIA, the return leg
- Delta Air Lines on MIA to BOS70.0%
- Spirit Airlines on MIA to BOS54.3%
- American Airlines network-wide record
- Miami International (MIA) delay statistics
- Boston Logan International (BOS) delay statistics
- Why the first flight of the morning is statistically safest
- How often a connection fails at the major US hubs
Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.