Airport month record

IADDEC

Washington Dulles International in December 2025

Departures: 4,676
Month: December 2025
National, same month: 73.2%
Carriers: 10

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

IAD in December sits in the middle of the pack with a C+. Close to three flights in four arrive on time by the DOT's definition, 2 points better than the national rate of 73.2%. The late ones land a little over an hour behind schedule. That rests on 4,676 flights, of which United Airlines flew 2,867 at 78.4% on time.

On time

74.8%

Arrivals under 15 minutes late, of 4,630 completed departures

Avg delay

69 min

Across delayed arrivals only, not all flights

Cancelled

0.71%

Nationally in December: 1.55%

Whole year

81.1%

IAD across all twelve months

These figures cover 4,676 departures from Washington Dulles International in December 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

December next to IAD's other months

Against IAD's own year, December ran 6 points worse than the twelve-month rate of 81.1%, which makes it number eleven of twelve months, best first. Cancellations were unusually low for IAD in December, at 0.71% against 1.37% across the year. Either side of it, November ran 81.8% on time and January 83.0%, so a trip moved by a few weeks would have landed in a better stretch.

IAD month by month
Month	Flights	On time	Avg delay	Cancelled	Grade
July 2025	5,248	69.5%	102 min	2.88%	C
August 2025	5,201	81.0%	70 min	0.79%	B+
September 2025	4,815	86.8%	67 min	0.27%	A+
October 2025	4,854	84.6%	64 min	0.27%	B+
November 2025	4,589	81.8%	71 min	1.46%	B
December 2025 (this page)	4,676	74.8%	69 min	0.71%	C+
January 2026	4,248	83.0%	82 min	5.65%	B−
February 2026	4,037	83.3%	74 min	1.34%	B
March 2026	4,983	79.6%	92 min	1.81%	B
April 2026	4,843	87.2%	71 min	0.31%	A+
May 2026	5,474	84.1%	78 min	0.57%	B+
June 2026	5,053	78.1%	85 min	0.93%	B+

Departure window

The best time of day to leave IAD in December

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 13 points, against 5 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am451 flights75.7%
8am–11am1,208 flights80.3%
11am–2pm890 flights76.6%
2pm–5pm272 flights74.5%
5pm–8pm1,310 flights67.4%
8pm–5am545 flights76.8%

Scale runs 60% to 85%. Rows with fewer than 30 flights show a dash.

Book the morning departure. Flights leaving between 8am–11am arrive on time 80.3% of the time, against 67.4% for the evening window. That is 13 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 5pm–8pm window is the busiest, with 1,310 flights scheduled in it.

Across the week, Wednesday is the strongest day at 85.4% on time and Friday the weakest at 59.0%. 26 points is a smaller lever than departure hour, but it is free.

Carrier by carrier

Which airlines ran best at IAD in December

The two carriers here are closely matched: 5 points separate the best from the worst. At that spread, schedule and price are better tie-breakers than reliability. Sample sizes are shown so you can see which rows are worth weighing.

Carriers at IAD in December 2025
Airline	Flights	On time	Avg delay	Cancelled	Grade
United Airlines	2,867	78.4%	62 min	0.10%	B+
Republic Airways	852	73.5%	67 min	1.29%	C
Delta Air Linesthin sample	243	68.8%	69 min	3.29%	C−
SkyWest Airlinesthin sample	167	62.7%	170 min	5.39%	D−
Frontier Airlinesthin sample	121	64.7%	84 min	0.83%	D+
Southwest Airlinesthin sample	104	66.0%	51 min	0.96%	C+
American Airlinesthin sample	97	71.1%	85 min	0.00%	C+
PSA Airlinesthin sample	89	69.7%	61 min	0.00%	C+
Alaska Airlinesthin sample	82	39.5%	39 min	0.00%	F+
Allegiant Airthin sample	54	68.5%	100 min	0.00%	C+

No carrier stands out. United tops the table at 78.4%, 5 points clear of the bottom, which is inside the range this kind of sample moves year to year.

Route by route

Busiest routes out of IAD in December

Routes from IAD in December 2025
Route	Flights	On time	Avg delay	Cancelled	Grade
IAD to ATL · Atlantathin sample	321	71.7%	79 min	2.49%	C
IAD to DEN · Denverthin sample	304	77.1%	66 min	0.33%	B+
IAD to SFO · San Franciscothin sample	245	68.9%	84 min	0.00%	C+
IAD to LAX · Los Angelesthin sample	215	85.9%	50 min	0.93%	A+
IAD to CLT · Charlottethin sample	177	68.9%	67 min	0.00%	C+
IAD to MCO · Orlandothin sample	172	76.7%	50 min	0.00%	B+
IAD to ORD · Chicagothin sample	146	75.3%	60 min	0.00%	B+
IAD to IAH · Houstonthin sample	139	77.7%	66 min	0.00%	B+
IAD to DFW · Dallas-Fort Worththin sample	138	69.6%	68 min	0.00%	C+
IAD to EWR · Newarkthin sample	125	75.2%	73 min	0.00%	B+
IAD to SEA · Seattlethin sample	124	48.4%	44 min	0.81%	F+
IAD to SAN · San Diegothin sample	122	78.3%	55 min	0.00%	B+
IAD to BOS · Bostonthin sample	122	76.2%	52 min	0.00%	B+
IAD to RDU · Raleighthin sample	120	76.7%	49 min	0.00%	B+
IAD to TPA · Tampathin sample	114	80.7%	47 min	0.00%	B+
IAD to PHX · Phoenixthin sample	108	82.4%	43 min	0.00%	B+
IAD to LGA · New Yorkthin sample	107	68.6%	88 min	4.67%	C−
IAD to PIT · Pittsburghthin sample	102	77.5%	53 min	0.00%	B+
IAD to LAS · Las Vegasthin sample	92	91.3%	64 min	0.00%	A+
IAD to BDL · Hartfordthin sample	90	86.7%	52 min	0.00%	A+
IAD to SJU · San Juanthin sample	77	62.3%	79 min	0.00%	D+
IAD to AUS · Austinthin sample	77	76.6%	49 min	0.00%	B+
IAD to ORF · Norfolkthin sample	76	70.7%	74 min	1.32%	C
IAD to FLL · Fort Lauderdalethin sample	76	76.3%	70 min	0.00%	B+
IAD to MSP · Minneapolisthin sample	76	72.4%	77 min	0.00%	C+

Delay causes

What held IAD up in December

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 81,000 reported delay minutes.

Late-arriving aircraft
35%
Carrier
32%
National Airspace System
29%
Extreme weather
4%
Security
0%

35% 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 81,000 reported delay minutes here, that single category outweighs weather by 8 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 80,883 reported delay minutes.

Cancellations are rare at 0.71%, below the national 1.55% 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.

8.2% of arrivals land an hour or more late, close to the national 10.0%. 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 a little over an hour, which a normal layover absorbs.

What to do with this

Flying from IAD in December

For a December trip through IAD: plan on this being one of the airport's harder months. The 8am–11am departures held up best at 80.3% on time, and with 8.2% of arrivals an hour or more late, a connection here deserves more slack than the same trip in April would.

Washington Dulles International (IAD), the whole year
IAD in July69.5%
IAD in August81.0%
IAD in September86.8%
IAD in October84.6%
IAD in November81.8%
IAD in January83.0%
IAD in February83.3%
IAD in March79.6%
IAD in April87.2%
IAD in May84.1%
IAD in June78.1%

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