Route reliability record
BWI→SJU
Baltimore to San Juan
- Flights
- 1,183
- Period
- July 2025 to June 2026
- Distance
- 1,565 mi
- Carriers
- 3
This route draws a C. About one flight in three arrives at least 15 minutes late, and the typical late arrival is about an hour behind schedule. Build slack into anything you connect to. That rests on 1,183 BWI to SJU flights, with a median arrival 5 minutes late.
Best time to fly BWI to SJU: a 8am–11am departure, ideally on a Wednesday. Flights in that window arrived on time 77.4% of the time and Wednesday flights 78.6%, against 66.6% for the route overall.
The national on-time rate over the same period is 77.6%, so this route runs 11 points behind the country as a whole. Across a thousand flights that is about 110 extra late arrivals.
Key figures
On time
66.6%
Arrivals under 15 minutes late, of 1,153 completed flights
Avg delay
67 min
Across delayed arrivals only, not all flights
Cancelled
2.54%
National rate is 1.81%
Best carrier
Southwest
67.9% on time across 821 flights
These figures cover 1,183 flights between July 2025 and June 2026. Beyond the headline rate, 10.4% 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
Which airline is most reliable on BWI to SJU
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 |
|---|---|---|---|---|---|
| Spirit Airlinesthin sample | 205 | 71.5% | 66 min | 5.85% | C− |
| Southwest Airlines | 821 | 67.9% | 56 min | 0.85% | C+ |
| Frontier Airlinesthin sample | 157 | 52.7% | 114 min | 7.01% | F− |
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–8am143 flights76.1%
- 8am–11am362 flights77.4%
- 11am–2pm162 flights59.9%
- 2pm–5pm40 flights70.0%
- 5pm–8pm275 flights60.9%
- 8pm–5am201 flights52.8%
Scale runs 45% to 85%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is where this operation falls apart: 52.8% on time, against 77.4% for the 8am–11am 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 362 flights scheduled in it.
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.
July is the worst month at 55.9% on time, 21 points below September, the best at 77.1%. 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. July was the busiest month here, with 141 flights.
Across the week, Wednesday is the strongest day at 78.6% on time and Sunday the weakest at 59.3%. 19 points is a smaller lever than departure hour, but it is free.
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 26,000 reported delay minutes.
- 37%Carrier
- 29%Late-arriving aircraft
- 24%National Airspace System
- 9%Extreme weather
- 1%Security
The largest share of delay minutes, 37%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. Unlike weather, that is a management outcome, and it is the category where the gap between two carriers on the same schedule is genuinely earned. It accounts for 9,573 of the 26,000 delay minutes reported here. The split is drawn from 25,964 reported delay minutes.
The practical consequence: the 8am–11am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 77.4% on time here.
Cancellations run at 2.54%, 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.
Connections and stage length
What a delay here actually costs
For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 10.4% 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.
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 77.9% on time across 1,184 flights, 11 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 11 points of difference.
The sample behind these figures is 1,183 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 SJU 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. September runs 77.1% on time and July 55.9%, a swing of 21 points. If the dates move at all, move them out of July before you think about anything else. 1,153 completed flights over 12 months sit behind that.
Common questions
BWI to SJU questions
How often is BWI to SJU delayed?
About 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 33.4% of the 1,183 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.
How reliable is BWI to SJU compared with the rest of the country?
66.6% of flights arrive on time here against a national 77.6%, a difference of 11 points against it. That is worth a C on this site's grading scale.
What time of day has the fewest delays on BWI to SJU?
The 8am–11am departure window is the strongest at 77.4% on time. The 8pm–5am window is the weakest at 52.8%, 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 July delays on BWI to SJU?
July is the weakest month at 55.9% on time, compared with 77.1% in September. 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
- SJU to BWI — the return legseparate record
- Baltimore/Washington International Thurgood Marshall (BWI) delay statistics
- Luis Munoz Marin International (SJU) delay statistics
- Spirit Airlines on BWI to SJU71.5%
- Southwest Airlines on BWI to SJU67.9%
- Frontier Airlines on BWI to SJU52.7%
- BWI to ATL, a related route80.6%
- MCO to SJU, a related route73.0%
- BWI to MCO, a related route75.6%
- Spirit Airlines on-time record71.5%
- Southwest Airlines on-time record67.9%
- Frontier Airlines on-time record52.7%
- The US routes with the most cancellations
- What a cancellation rate actually tells you (and what it hides)
Direction matters. BWI to SJU and SJU to BWI are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
Embed BWI to SJU’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, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.