Airport month record

BWISEP

Baltimore/Washington International Thurgood Marshall in September 2025

Departures: 7,968
Month: September 2025
National, same month: 83.4%
Carriers: 9

Historical statistics for September 2025, not live status or a forecast for this year’s September. For today’s conditions at BWI, see live FAA status.

BWI in September earns an A+. More than four flights in five arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 2 points better than the national rate of 83.4%. When something does go wrong the average delay runs about an hour. That rests on 7,968 flights, of which Delta Air Lines flew 453 at 92.1% on time.

Delta Air Lines is the most reliable of the three carriers covered here at 92.1% on time across 453 flights.

On time

85.5%

Arrivals under 15 minutes late, of 7,941 completed departures

Avg delay

56 min

Across delayed arrivals only, not all flights

Cancelled

0.18%

Nationally in September: 0.51%

Whole year

77.6%

BWI across all twelve months

These figures cover 7,968 departures from Baltimore/Washington International Thurgood Marshall in September 2025. On time means an arrival less than 15 minutes after the scheduled gate time, the DOT's threshold, and the national comparison uses every US departure in the same month rather than the whole year.

Against the year

September next to BWI's other months

Against BWI's own year, September ran 8 points better than the twelve-month rate of 77.6%, which makes it the best of the twelve months in the data. Cancellations were unusually low for BWI in September, at 0.18% against 1.71% across the year. Either side of it, August ran 78.8% on time and October 81.4%, so a trip moved by a few weeks would have landed in a worse stretch.

BWI month by month
Month	Flights	On time	Avg delay	Cancelled	Grade
July 2025	8,922	66.2%	92 min	3.64%	C−
August 2025	8,381	78.8%	62 min	0.76%	B+
September 2025 (this page)	7,968	85.5%	56 min	0.18%	A+
October 2025	8,475	81.4%	49 min	0.14%	B+
November 2025	7,721	82.9%	62 min	1.80%	B
December 2025	7,863	70.4%	54 min	1.27%	C
January 2026	6,934	82.9%	53 min	5.61%	B−
February 2026	6,552	83.1%	58 min	3.59%	B−
March 2026	7,803	74.6%	69 min	2.58%	C
April 2026	8,041	79.9%	55 min	0.34%	B+
May 2026	8,161	76.7%	59 min	0.28%	B+
June 2026	8,045	70.9%	63 min	1.16%	C

Departure window

The best time of day to leave BWI in September

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 18 points, against 7 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am1,113 flights93.1%
8am–11am1,794 flights93.1%
11am–2pm1,092 flights88.3%
2pm–5pm1,454 flights82.9%
5pm–8pm1,497 flights74.7%
8pm–5am1,018 flights80.1%

Scale runs 65% to 100%. Rows with fewer than 30 flights show a dash.

Book the early departure. Flights leaving between 5am–8am arrive on time 93.1% of the time, against 74.7% for the evening window. That is 18 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 8am–11am window is the busiest, with 1,794 flights scheduled in it.

Across the week, Tuesday is the strongest day at 91.3% on time and Thursday the weakest at 76.8%. 15 points is a smaller lever than departure hour, but it is free.

Carrier by carrier

Which airlines ran best at BWI in September

The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 92.1% of the time; Southwest Airlines manages 85.4%. Sample sizes sit next to every figure, because a two-point gap across 5,998 flights means less than a ten-point one.

Carriers at BWI in September 2025
Airline	Flights	On time	Avg delay	Cancelled	Grade
Southwest Airlines	5,998	85.4%	51 min	0.05%	A+
Delta Air Lines	453	92.1%	89 min	0.00%	A+
Spirit Airlines	429	87.9%	74 min	1.17%	A
United Airlinesthin sample	363	85.9%	62 min	0.00%	A+
American Airlinesthin sample	257	89.4%	79 min	0.78%	A+
Frontier Airlinesthin sample	219	77.5%	66 min	0.46%	B+
Republic Airwaysthin sample	100	64.9%	71 min	3.00%	D
Envoy Airthin sample	87	77.0%	48 min	0.00%	B+
Alaska Airlinesthin sample	60	85.0%	53 min	0.00%	A+

Delta leads Southwest by 7 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.

Route by route

Busiest routes out of BWI in September

Routes from BWI in September 2025
Route	Flights	On time	Avg delay	Cancelled	Grade
BWI to ATL · Atlanta	465	88.2%	55 min	0.00%	A+
BWI to MCO · Orlandothin sample	342	87.0%	55 min	0.58%	A+
BWI to BOS · Bostonthin sample	288	60.2%	83 min	1.39%	D
BWI to DEN · Denverthin sample	266	83.8%	55 min	0.00%	B+
BWI to CLT · Charlottethin sample	252	89.2%	79 min	0.40%	A+
BWI to ORD · Chicagothin sample	248	81.9%	58 min	0.00%	B+
BWI to FLL · Fort Lauderdalethin sample	236	84.1%	57 min	0.85%	B+
BWI to DTW · Detroitthin sample	218	87.5%	64 min	0.92%	A+
BWI to TPA · Tampathin sample	200	89.5%	47 min	0.00%	A+
BWI to MDW · Chicagothin sample	181	86.1%	48 min	0.55%	A+
BWI to PVD · Providencethin sample	172	86.0%	55 min	0.00%	A+
BWI to LAX · Los Angelesthin sample	169	81.4%	49 min	0.59%	B+
BWI to LAS · Las Vegasthin sample	168	82.0%	55 min	0.00%	B+
BWI to BNA · Nashvillethin sample	167	89.2%	54 min	0.00%	A+
BWI to DAL · Dallasthin sample	159	85.4%	54 min	0.00%	A+
BWI to MIA · Miamithin sample	155	90.2%	45 min	0.00%	A+
BWI to BUF · Buffalothin sample	147	87.1%	34 min	0.00%	A+
BWI to ALB · Albanythin sample	146	85.6%	34 min	0.00%	A+
BWI to BDL · Hartfordthin sample	146	90.4%	37 min	0.00%	A+
BWI to MHT · Manchesterthin sample	146	89.0%	36 min	0.00%	A+
BWI to RDU · Raleighthin sample	142	89.4%	77 min	0.00%	A+
BWI to ORF · Norfolkthin sample	137	89.8%	39 min	0.00%	A+
BWI to MSP · Minneapolisthin sample	129	86.0%	73 min	0.00%	A+
BWI to HOU · Houstonthin sample	125	84.8%	49 min	0.00%	B+
BWI to PWM · Portlandthin sample	121	87.6%	38 min	0.00%	A+

Delay causes

What held BWI up in September

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 64,000 reported delay minutes.

Late-arriving aircraft
37%
Carrier
32%
National Airspace System
26%
Extreme weather
5%
Security
0%

37% 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 64,000 reported delay minutes here, that single category outweighs weather by 7 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 64,311 reported delay minutes.

Cancellations are rare at 0.18%, below the national 0.51% and low enough to earn the plus on the grade. Roughly one flight in 100 is called off; the risk here is arriving late, not not arriving.

Badly late arrivals are rare here: only 3.9% land an hour or more behind schedule, against 5.4% nationally. Connections built on this flight are about as safe as US domestic connections get, though a cancelled flight still ignores every layover you give it.

What to do with this

Flying from BWI in September

For a September trip through BWI: this is one of the better months to be flying from here, 85.5% on time with 0.18% cancelled. That is a base rate for the month as a whole; a single storm can still spoil a particular day.

Baltimore/Washington International Thurgood Marshall (BWI), the whole year
BWI in July66.2%
BWI in August78.8%
BWI in October81.4%
BWI in November82.9%
BWI in December70.4%
BWI in January82.9%
BWI in February83.1%
BWI in March74.6%
BWI in April79.9%
BWI in May76.7%
BWI in June70.9%

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