Route reliability record
MIA→BOS
Miami to Boston
- Flights
- 3,366
- Period
- September 2025 to August 2026
- Distance
- 1,258 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, 8 points worse than the national rate of 77.3%. The late ones land a little over an hour behind schedule. That rests on 3,366 MIA to BOS flights, of which American Airlines flew 2,271 at 71.1% on time.
Best time to fly MIA to BOS: a 5am–8am departure, ideally on a Wednesday. Flights in that window arrived on time 89.5% of the time and Wednesday flights 74.5%, against 69.8% for the route overall.
The national on-time rate over the same period is 77.3%, so this route runs 8 points behind the country as a whole. Across a thousand flights that is about 75 extra late arrivals.
Key figures
On time
69.8%
Arrivals under 15 minutes late, of 3,283 completed flights
Avg delay
72 min
Across delayed arrivals only, not all flights
Cancelled
2.20%
National rate is 1.89%
Best carrier
American
71.1% on time across 2,271 flights
These figures cover 3,366 flights between September 2025 and August 2026. Beyond the headline rate, 11.7% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
Fare search by Aviasales, a Travelpayouts partner. Booking through it may earn this site a commission at no cost to you; it changes no figure here.
Carrier by carrier
Which airline is most reliable on MIA to BOS
The two carriers here are closely matched: 2 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.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Envoy Airthin sample | 1 | 100.0% | — | 0.00% | A+ |
| Republic Airwaysthin sample | 25 | 76.0% | 131 min | 0.00% | B+ |
| American Airlines | 2,271 | 71.1% | 70 min | 1.67% | C |
| Delta Air Lines | 890 | 69.6% | 78 min | 2.70% | C |
| Spirit Airlinesthin sample | 175 | 54.3% | 70 min | 6.86% | F− |
| JetBlue Airwaysthin sample | 4 | 25.0% | 67 min | 0.00% | F+ |
No carrier stands out. American tops the table at 71.1%, 2 points clear of the bottom, which is inside the range this kind of sample moves year to year.
Flight by flight
Flights on MIA to BOS
The flight numbers below flew this route at least 250 times in the period, busiest first. Each has its own record, with its schedule and delay causes.
Timetable by Aviasales, a Travelpayouts partner. Booking through it may earn this site a commission at no cost to you; it changes no figure here.
Best ways to make this trip
The most reliable ways to fly Miami to Boston
Every airline on this route and on the routes between nearby airports, ranked by how often a scheduled flight actually operated and arrived on time. 3 of the top 5 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. MIA → BOSMiami to Boston | American Airlines | 69.9% | 71.1% | 1.67% | 5am–8am, Sat | AA 1074 17:35 |
| 2. FLL → BOSFort Lauderdale to Boston | Delta Air Lines | 69.8% | 72.1% | 3.16% | 5am–8am, Sat | — |
| 3. MIA → BOSMiami to Boston | Delta Air Lines | 67.7% | 69.6% | 2.70% | 5am–8am, Tue | — |
| 4. FLL → BOSFort Lauderdale to Boston | JetBlue Airways | 63.7% | 65.9% | 3.37% | 5am–8am, Wed | B6 470 20:00 |
| 5. FLL → BOSFort Lauderdale to Boston | Spirit Airlines | 56.4% | 60.0% | 6.04% | 8am–11am, Wed | — |
Success is the share of scheduled flights that operated and arrived less than 15 minutes late, so a cancelled flight counts against it. “(route)” means the best time comes from every carrier on the route rather than this airline alone.
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 31 points, against 2 points between the best and worst carrier.
- 5am–8am390 flights89.5%
- 8am–11am548 flights85.9%
- 11am–2pm739 flights68.2%
- 2pm–5pm222 flights69.0%
- 5pm–8pm561 flights60.3%
- 8pm–5am906 flights59.0%
Scale runs 50% to 95%.
The 8pm–5am window is where this operation falls apart: 59.0% on time, against 89.5% 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 906 flights scheduled in it.
Explore
Filter MIA to BOS by airline, time, month and day
Pick a breakdown and a carrier. The dashed mark on each row is the same slice for every US flight.
On MIA to BOS, the best departure window is 5am–8am at 89.5% on time and the worst is 8pm–5am at 59.0%, a wide gap of 30.5 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am89.5%
- 8–11am85.9%
- 11am–2pm68.2%
- 2–5pm69.0%
- 5–8pm60.3%
- 8pm–5am59.0%
best all US flightsScale 50% to 95%.
Across the year
When delays peak on this route
This route's year swings by 21 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.
May is the best month on the calendar at 77.4% on time. Shoulder season thins the schedule and takes the summer weather with it, and the operation gets its margin back. April was the busiest month here, with 333 flights.
Across the week, Wednesday is the strongest day at 74.5% on time and Monday the weakest at 63.5%, a spread of 11 points.
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 71,000 reported delay minutes.
- 41%Late-arriving aircraft
- 30%Carrier
- 25%National Airspace System
- 4%Extreme weather
- 0%Security
41% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 71,000 reported delay minutes here, that single category outweighs weather by 10 to one. The split is drawn from 71,495 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 89.5% on time here.
Cancellations sit at 2.20% against a national 1.89%, which is ordinary. Diversions add another 0.27%.
Connections and stage length
What a delay here actually costs
11.7% of arrivals land a full hour or more behind schedule, against 8.3% nationally. Ninety minutes is the honest minimum for a connection 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.
The return leg is a different operation and performs like one: it runs 78.0% on time across 3,368 flights, 8 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 8 points of difference.
The sample behind these figures is 3,366 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.
Work out the risk of missing a connection in BOS after this flight
What to do with this
Booking this route
Put together: the calendar is the biggest lever here, not the carrier or the hour. May runs 77.4% on time and October 56.9%, a swing of 21 points. If the dates move at all, move them out of October before you think about anything else. 3,283 completed flights over 12 months sit behind that.
Common questions
MIA to BOS questions
How often is MIA to BOS delayed?
Roughly one flight in three arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 30.2% of the 3,366 flights in this analysis, against 22.7% nationally. Delayed flights are late by a little over an hour on average.
Which airline is most reliable on MIA to BOS?
American Airlines leads at 71.1% on time across 2,271 flights. Delta Air Lines is at the other end on 69.6%, a gap of 2 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 MIA to BOS?
The 5am–8am departure window is the strongest at 89.5% on time. The 8pm–5am window is the weakest at 59.0%, 31 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 October delays on MIA to BOS?
October is the weakest month at 56.9% on time, compared with 77.4% in May. Across the year that is 21 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 MIA — the return legseparate record
- Miami International (MIA) delay statistics
- Boston Logan International (BOS) delay statistics
- American Airlines on MIA to BOS71.1%
- Delta Air Lines on MIA to BOS69.6%
- Spirit Airlines on MIA to BOS54.3%
- MIA to ATL, a related route74.2%
- DCA to BOS, a related route70.1%
- MIA to LGA, a related route67.4%
- Envoy Air on-time record100.0%
- Republic Airways on-time record76.0%
- American Airlines on-time record71.1%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.05 million flight records
Direction matters. MIA to BOS and BOS to MIA are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
Embed MIA to BOS’s on-time badge on your site
Paste this into a web page. The badge shows the current on-time rate, cancellation rate and grade, and updates every month. Preview it, or build a badge for another route or airport.
Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.