Carrier route record

F9BWI→SJU

Frontier Airlines · Baltimore to San Juan

Flights: 157
Period: July 2025 to June 2026
Share of route: 13%
Carriers: 3

Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Frontier Airlines.

Frontier on BWI to SJU earns an F−, which is as low as this site's scale goes for a reason. Only 52.7% of flights arrive inside the 15-minute window, 25 points worse than the national rate of 77.6%. Late arrivals average close to two hours. Treat any tight connection here as a coin flip. That rests on 157 flights, with a median arrival 13 minutes late.

The national on-time rate over the same period is 77.6%, so Frontier on BWI to SJU runs 25 points behind the country as a whole. Across a thousand flights that is about 249 extra late arrivals.

On time

52.7%

Arrivals under 15 minutes late, of 146 completed flights

Avg delay

114 min

Across delayed arrivals only, not all flights

Cancelled

7.01%

National rate is 1.81%

Whole route

66.6%

Every carrier on BWI to SJU, 1,183 flights

These figures cover 157 flights between July 2025 and June 2026. Beyond the headline rate, 26.0% 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

Frontier against every carrier on BWI to SJU

Frontier flew 157 of the 1,183 flights on BWI to SJU, about 13% of it. Its 52.7% on time is 14 points worse than the route as a whole, which runs 66.6%. Ranked by on-time rate it is last of three carriers on the route, where the range runs from Spirit at 71.5% to Frontier at 52.7%. One 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.

On-time performance by carrier on BWI to SJU
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 Airlines (this page)thin sample	157	52.7%	114 min	7.01%	F−

Departure window

When Frontier runs best on this route

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 23 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–8am—
8am–11am10 flights—
11am–2pm67 flights44.1%
2pm–5pm3 flights—
5pm–8pm26 flights—
8pm–5am51 flights66.7%

Scale runs 35% to 70%. Rows with fewer than 30 flights show a dash.

The weak window here is the middle of the day, not the evening: 11am–2pm runs 44.1% on time against 66.7% for 8pm–5am. That shape usually means a departure bank rather than an accumulating delay, so the recovery later in the afternoon is real rather than noise. The 11am–2pm window is the busiest, with 67 flights scheduled in it.

Across the year

Frontier on BWI to SJU through the year

Jul–Sep 202536 flights36.4%
Oct–Dec 202532 flights56.7%
Jan–Mar 202631 flights—
Apr–Jun 202658 flights59.6%

Scale runs 30% to 65%. Rows with fewer than 30 flights show a dash.

Monthly volumes are too low here to break the year into twelve reliable readings. What the twelve-month total says is 52.7% on time across 157 flights.

Frontier on BWI to SJU did not run the same all year. Its best quarter was Apr–Jun 2026 at 59.6% on time and its weakest Jul–Sep 2025 at 36.4%, a swing of 23 points on roughly 52 flights a quarter. The twelve-month rate averages over that, so if you are flying in a weak quarter the quarter's own figure is the better guide.

Delay causes

Why Frontier runs late on this route

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 7,848 reported delay minutes.

Carrier
39%
Late-arriving aircraft
26%
National Airspace System
19%
Extreme weather
17%

Extreme weather accounts for 17% of delay minutes, well above the single-digit share typical across the system. Weather delays are lumpy: they arrive as whole bad days rather than as a steady drag, so the monthly strip above is the more useful view of the risk. The national share is 6%, so this operation carries roughly 2.6 times the usual weather exposure. The split is drawn from 7,848 reported delay minutes.

The largest share of delay minutes, 39%, 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 3,083 of the 7,848 delay minutes reported here.

Cancellations run at 7.01%, against 1.81% nationally. That is about one flight in fifteen 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 costs

For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 26.0% 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 69.4% on time across 157 flights, 17 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 17 points of difference.

One caution: this is a thin sample. 157 flights over twelve months is enough to clear this site's floor but not enough to pin the rate down tightly, and a single bad week moves it by more than a point. Treat the grade as a rough reading.

What to do with this

Booking Frontier on BWI to SJU

Put together: the delay figures matter less here than the 7.01% cancellation rate. A late arrival costs you close to two hours; a cancelled flight costs you the day. Book the 8pm–5am departure so there is still a schedule behind you if it goes wrong, and treat a same-day connection as optimistic. 146 completed flights over 12 months sit behind that.

Where to go next

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.

Key figures