Route reliability record
SJU→BWI
San Juan to Baltimore
- Flights
- 1,184
- Period
- July 2025 to June 2026
- Distance
- 1,565 mi
- Carriers
- 3
This route lands a B, level with the national rate of 77.6%. Roughly one flight in five arrives 15 minutes late or worse, and those flights are late by about an hour on average. That is a workable record, not a spotless one. That rests on 1,184 SJU to BWI flights, with a median arrival 2 minutes early.
Best time to fly SJU to BWI: a 5am–8am departure, ideally on a Wednesday. Flights in that window arrived on time 88.5% of the time and Wednesday flights 82.6%, against 77.9% for the route overall.
The US average over the same twelve months is 77.6%, 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
77.9%
Arrivals under 15 minutes late, of 1,151 completed flights
Avg delay
60 min
Across delayed arrivals only, not all flights
Cancelled
2.45%
National rate is 1.81%
Best carrier
Southwest
80.3% on time across 822 flights
These figures cover 1,184 flights between July 2025 and June 2026. The median arrival is 2 minutes early, which is the part an average hides: most flights here are fine, and the on-time rate is decided by a tail of badly late ones. On-time means under 15 minutes late, the DOT's own threshold.
Carrier by carrier
Which airline is most reliable on SJU to BWI
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 |
|---|---|---|---|---|---|
| Southwest Airlines | 822 | 80.3% | 48 min | 0.97% | B+ |
| Spirit Airlinesthin sample | 205 | 74.3% | 106 min | 6.34% | C− |
| Frontier Airlinesthin sample | 157 | 69.4% | 53 min | 5.10% | C− |
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 25 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–8am445 flights88.5%
- 8am–11am106 flights78.8%
- 11am–2pm72 flights77.1%
- 2pm–5pm267 flights74.5%
- 5pm–8pm164 flights65.0%
- 8pm–5am130 flights63.6%
Scale runs 55% to 95%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is where this operation falls apart: 63.6% on time, against 88.5% 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 5am–8am window is the busiest, with 445 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 29 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.
October is the best month on the calendar at 93.3% on time. Shoulder season thins the schedule and takes the summer weather with it, and the operation gets its margin back. July was the busiest month here, with 142 flights.
Across the week, Wednesday is the strongest day at 82.6% on time and Friday the weakest at 73.0%. 10 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
One category carries most of the weight here. Late-arriving aircraft accounts for 46% of the 15,000 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.
- 46%Late-arriving aircraft
- 33%Carrier
- 20%National Airspace System
- 1%Extreme weather
- 0%Security
46% 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 15,000 reported delay minutes here, that single category outweighs weather by 46 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 15,216 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 88.5% on time here.
Cancellations sit at 2.45% against a national 1.81%, which is ordinary. Diversions add another 0.34%.
Connections and stage length
What a delay here actually costs
5.5% of arrivals land an hour or more late, close to the national 8.1%. That is the figure that decides a connection, and it says a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last about an hour, which a normal layover absorbs.
At 1,565 miles this is transcontinental flying, and long routes get a quiet structural advantage. Scheduled block time on a flight this length carries more padding in absolute minutes, so a twenty-minute late departure often still becomes an on-time arrival. Read the on-time rate here as slightly flattering next to a short-haul route with the same operational quality.
The return leg is a different operation and performs like one: it runs 66.6% on time across 1,183 flights, 11 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 11 points of difference.
The sample behind these figures is 1,184 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 BWI 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. October runs 93.3% on time and March 64.1%, a swing of 29 points. If the dates move at all, move them out of March before you think about anything else. 1,151 completed flights over 12 months sit behind that.
Common questions
SJU to BWI questions
How often is SJU to BWI 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 22.1% of the 1,184 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.
How reliable is SJU to BWI compared with the rest of the country?
77.9% of flights arrive on time here against a national 77.6%, a difference of half a point in its favour. That is worth a B on this site's grading scale.
What time of day has the fewest delays on SJU to BWI?
The 5am–8am departure window is the strongest at 88.5% on time. The 8pm–5am window is the weakest at 63.6%, 25 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 March delays on SJU to BWI?
March is the weakest month at 64.1% on time, compared with 93.3% in October. Across the year that is 29 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
- BWI to SJU — the return legseparate record
- Luis Munoz Marin International (SJU) delay statistics
- Baltimore/Washington International Thurgood Marshall (BWI) delay statistics
- Southwest Airlines on SJU to BWI80.3%
- Spirit Airlines on SJU to BWI74.3%
- Frontier Airlines on SJU to BWI69.4%
- SJU to MCO, a related route78.9%
- ATL to BWI, a related route75.6%
- SJU to JFK, a related route79.3%
- Southwest Airlines on-time record80.3%
- Spirit Airlines on-time record74.3%
- Frontier Airlines on-time record69.4%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
Direction matters. SJU to BWI and BWI to SJU 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, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.