Washington Dulles International in May 2026

86.2%departed on time

BTS: A flight is counted as on time if it arrived less than 15 minutes after its scheduled time. Only carriers with at least 0.5 percent of domestic scheduled passenger revenue report.

In May 2026, reporting carriers scheduled 5,474 domestic departures from Washington Dulles International (IAD). 86.2% left less than 15 minutes late and 83.4% reached their destination on time; 0.6% were cancelled.

Nationally that month, 77.1% of flights departed on time and 77.6% arrived on time, so IAD departures were 9.1 points above the national departure figure.

A year earlier, in May 2025, the airport had 5,491 departures with 80.2% leaving on time: a change of +6.0 points, with flights down 0%.

Flights arriving at IAD that month were on time 85.1% of the time (5,449 scheduled arrivals).

Of the delay minutes that carriers assigned to a BTS cause category that month, late-arriving aircraft 36%, air carrier 32% and national aviation system 25%.

On time 83.4%
Arrived 15+ minutes late 15.8%
Cancelled 0.6%
Diverted 0.3%

Every scheduled departure from IAD in May 2026, judged by arrival at the destination.

May 2026 against a year earlier, the airport's year and the nation

Measure	May 2026	May 2025	IAD, 12 months to Jul 2026	All reported flights, May 2026
Departed on time	86.2%	80.2%	82.6%	77.1%
Arrived on time	83.4%	73.4%	80.1%	77.6%
Cancelled	0.6%	0.6%	1.4%	0.9%
Average departure delay (late minutes only)	12.7 min	16.5 min	14.7 min	16.0 min
Scheduled departures a day	183	183	159	20,391
Scheduled departures	5,474	5,491	58,031	611,735

Airlines that month

Reporting carrier	Flights	Share	On time	Avg arrival delay	Cancelled
UA United Airlines	3,541	65%	84.7%	-0.3 min	0.2%
YX Republic Airline	718	13%	83.8%	3.2 min	1.5%
DL Delta Air Lines	299	5%	81.9%	1.5 min	2.3%
OO SkyWest Airlines	259	5%	83.4%	20.5 min	0.4%
F9 Frontier Airlines	167	3%	73.1%	10.9 min	0.0%
AA American Airlines	162	3%	71.6%	14.7 min	1.9%
AS Alaska Airlines	120	2%	84.2%	-2.5 min	0.0%
WN Southwest Airlines	93	2%	71.0%	4.1 min	0.0%
OH PSA Airlines	67	1%	83.6%	28.7 min	1.5%
G4 Allegiant Air	48	1%	83.3%	15.9 min	0.0%

Busiest routes that month

Route	Cities	Flights	On time	Avg arrival delay	Cancelled
IAD–ATL	Washington to Atlanta	405	74.3%	5.3 min	1.5%
IAD–DEN	Washington to Denver	316	84.2%	-1.7 min	0.0%
IAD–SFO	Washington to San Francisco	268	79.5%	5.1 min	0.0%
IAD–LAX	Washington to Los Angeles	252	87.3%	-5.9 min	0.4%
IAD–ORD	Washington to Chicago	217	76.5%	8.2 min	0.0%
IAD–SEA	Washington to Seattle	201	86.1%	-1.8 min	0.0%
IAD–MCO	Washington to Orlando	197	85.8%	-1.7 min	0.0%
IAD–DFW	Washington to Dallas/Fort Worth	175	72.0%	28.7 min	1.7%
IAD–CLT	Washington to Charlotte	174	85.6%	8.1 min	0.6%
IAD–IAH	Washington to Houston	167	82.6%	2.3 min	0.6%
IAD–DTW	Washington to Detroit	144	86.1%	6.2 min	1.4%
IAD–EWR	Washington to Newark	135	87.4%	-5.3 min	2.2%

By scheduled departure hour

On-time share:under 62%6270768288% and over

Share of departures that left less than 15 minutes late, by scheduled hour (local time), May 2026.

Delay causes

BTS cause category	Share of delay minutes	National, May 2026	Minutes
Air carrier	32.1%	33.0%	21,656
Late-arriving aircraft	36.1%	40.4%	24,366
National Aviation System	24.7%	20.5%	16,668
Extreme weather	7.2%	6.0%	4,853
Security	0.0%	0.1%	11

67,554 delay minutes on 864 flights that arrived 15 or more minutes late and carried a cause report. Carriers assign the categories; see what each category means.

Questions and answers

How many flights left IAD on time in May 2026?

86.2% of 5,474 scheduled domestic departures left less than 15 minutes late, and 83.4% reached their destination on time. The national figures that month were 77.1% and 77.6%.

How does that compare with a year earlier?

In May 2025, 80.2% of 5,491 departures left on time and 0.6% were cancelled, against 86.2% and 0.6% in May 2026.

Provenance

Source: Bureau of Transportation Statistics, Reporting Carrier On-Time Performance, file for May 2026; public domain. Domestic scheduled flights by reporting carriers, totals and averages only. The site's data runs through July 2026. Full record for IAD · methodology · corrections.