Route reliability record
BOS→MIA
Boston to Miami
- Flights
- 3,368
- Period
- September 2025 to August 2026
- Distance
- 1,258 mi
- Carriers
- 5
This route lands a B, level with the national rate of 77.3%. Roughly one flight in five arrives 15 minutes late or worse, and those flights are late by a little over an hour on average. That rests on 3,368 BOS to MIA flights, of which American Airlines flew 2,271 at 82.3% on time.
Best time to fly BOS to MIA: a 5am–8am departure, ideally on a Wednesday. Flights in that window arrived on time 91.1% of the time and Wednesday flights 83.7%, against 78.0% for the route overall.
The US average over the same twelve months is 77.3%, so there is little to separate this route from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
78.0%
Arrivals under 15 minutes late, of 3,289 completed flights
Avg delay
78 min
Across delayed arrivals only, not all flights
Cancelled
2.17%
National rate is 1.89%
Best carrier
American
82.3% on time across 2,271 flights
These figures cover 3,368 flights between September 2025 and August 2026. Beyond the headline rate, 8.6% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Carrier by carrier
Which airline is most reliable on BOS to MIA
The choice of carrier is not cosmetic here. American Airlines arrives on time 82.3% of the time; Delta Air Lines manages 72.4%. Sample sizes sit next to every figure, because a two-point gap across 892 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| JetBlue Airwaysthin sample | 4 | 100.0% | — | 0.00% | A+ |
| American Airlines | 2,271 | 82.3% | 77 min | 1.72% | B |
| Delta Air Lines | 892 | 72.4% | 78 min | 2.58% | C |
| Spirit Airlinesthin sample | 176 | 55.2% | 81 min | 6.25% | D− |
| Republic Airwaysthin sample | 25 | 44.0% | 70 min | 0.00% | F+ |
American leads Delta by 10 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.
Flight by flight
Flights on BOS to MIA
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.
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Best ways to make this trip
The most reliable ways to fly Boston to Miami
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. BOS → MIABoston to Miami | American Airlines | 80.9% | 82.3% | 1.72% | 5am–8am, Wed | AA 2980 06:00 |
| 2. BOS → MIABoston to Miami | Delta Air Lines | 70.5% | 72.4% | 2.58% | 5am–8am, Wed | DL 1399 07:05 |
| 3. BOS → FLLBoston to Fort Lauderdale | Delta Air Lines | 67.7% | 69.8% | 3.04% | 8am–11am, Wed | DL 1401 07:10 |
| 4. BOS → FLLBoston to Fort Lauderdale | JetBlue Airways | 64.1% | 66.4% | 3.50% | 5am–8am, Wed | B6 569 06:00 |
| 5. BOS → FLLBoston to Fort Lauderdale | Spirit Airlines | 58.1% | 62.1% | 6.47% | 5am–8am, Thu | — |
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 27 points, against 10 points between the best and worst carrier.
- 5am–8am1,212 flights91.1%
- 8am–11am282 flights84.9%
- 11am–2pm557 flights77.3%
- 2pm–5pm703 flights64.1%
- 5pm–8pm458 flights66.3%
- 8pm–5am156 flights64.2%
Scale runs 55% to 95%.
Book the early departure. Flights leaving between 5am–8am arrive on time 91.1% of the time, against 64.1% for the afternoon window. That is 27 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 5am–8am window is the busiest, with 1,212 flights scheduled in it.
Explore
Filter BOS to MIA 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 BOS to MIA, the best departure window is 5am–8am at 91.1% on time and the worst is 2pm–5pm at 64.1%, a wide gap of 27.0 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am91.1%
- 8–11am84.9%
- 11am–2pm77.3%
- 2–5pm64.1%
- 5–8pm66.3%
- 8pm–5am64.2%
best all US flightsScale 55% to 95%.
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.
December is the weak month at 69.9% on time, against 86.7% in June. 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. April was the busiest month here, with 334 flights.
Across the week, Wednesday is the strongest day at 83.7% on time and Sunday the weakest at 70.3%, a spread of 13 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 56,000 reported delay minutes.
- 38%Carrier
- 33%Late-arriving aircraft
- 27%National Airspace System
- 3%Extreme weather
- 0%Security
The largest share of delay minutes, 38%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 21,000 of the 56,000 delay minutes reported here. The split is drawn from 55,971 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 91.1% on time here.
Cancellations sit at 2.17% against a national 1.89%, which is ordinary. Diversions add another 0.18%.
Connections and stage length
What a delay here actually costs
8.6% of arrivals land an hour or more late, close to the national 8.3%, so a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last a little over an hour, which a normal layover absorbs.
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 69.8% on time across 3,366 flights, 8 points below 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 3,368 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 MIA 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. June runs 86.7% on time and December 69.9%, a swing of 17 points. If the dates move at all, move them out of December before you think about anything else. 3,289 completed flights over 12 months sit behind that.
Common questions
BOS to MIA questions
How often is BOS to MIA delayed?
Roughly one flight in five arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 22.0% of the 3,368 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 BOS to MIA?
American Airlines leads at 82.3% on time across 2,271 flights. Delta Air Lines is at the other end on 72.4%, 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 BOS to MIA?
The 5am–8am departure window is the strongest at 91.1% on time. The 2pm–5pm window is the weakest at 64.1%, 27 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 BOS to MIA?
December is the weakest month at 69.9% on time, compared with 86.7% in June. 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.
Related
Where to go next
- MIA to BOS — the return legseparate record
- Boston Logan International (BOS) delay statistics
- Miami International (MIA) delay statistics
- American Airlines on BOS to MIA82.3%
- Delta Air Lines on BOS to MIA72.4%
- Spirit Airlines on BOS to MIA55.2%
- BOS to DCA, a related route72.6%
- ATL to MIA, a related route71.2%
- BOS to ORD, a related route71.9%
- JetBlue Airways on-time record100.0%
- American Airlines on-time record82.3%
- Delta Air Lines on-time record72.4%
- 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. BOS to MIA and MIA to BOS are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
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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.