Ontario International in August 2025

80.9%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 August 2025, reporting carriers scheduled 2,291 domestic departures from Ontario International (ONT). 80.9% left less than 15 minutes late and 81.4% reached their destination on time; 0.8% were cancelled.

Nationally that month, 76.8% of flights departed on time and 76.3% arrived on time, so ONT departures were 4.1 points above the national departure figure.

A year earlier, in August 2024, the airport had 2,428 departures with 85.0% leaving on time: a change of −4.1 points, with flights down 6%.

Flights arriving at ONT that month were on time 76.9% of the time (2,291 scheduled arrivals).

Of the delay minutes that carriers assigned to a BTS cause category that month, late-arriving aircraft 42%, air carrier 34% and national aviation system 19%.

On time 81.4%
Arrived 15+ minutes late 17.4%
Cancelled 0.8%
Diverted 0.4%

Every scheduled departure from ONT in August 2025, judged by arrival at the destination.

August 2025 against a year earlier, the airport's year and the nation

Measure	Aug 2025	Aug 2024	ONT, 12 months to Jul 2026	All reported flights, Aug 2025
Departed on time	80.9%	85.0%	80.3%	76.8%
Arrived on time	81.4%	84.6%	81.2%	76.3%
Cancelled	0.8%	0.9%	0.9%	1.1%
Average departure delay (late minutes only)	13.9 min	10.3 min	13.7 min	17.6 min
Scheduled departures a day	76	81	71	20,079
Scheduled departures	2,291	2,428	25,854	602,378

Airlines that month

Reporting carrier	Flights	Share	On time	Avg arrival delay	Cancelled
WN Southwest Airlines	985	43%	84.7%	1.1 min	0.2%
AA American Airlines	295	13%	67.8%	30.7 min	2.4%
UA United Airlines	240	10%	77.5%	10.1 min	0.0%
F9 Frontier Airlines	222	10%	73.4%	9.2 min	2.3%
DL Delta Air Lines	196	9%	94.9%	-16.0 min	1.0%
AS Alaska Airlines	169	7%	81.1%	2.9 min	1.2%
OO SkyWest Airlines	153	7%	86.9%	-0.8 min	0.0%
B6 JetBlue Airways	31	1%	83.9%	-8.1 min	0.0%

Busiest routes that month

Route	Cities	Flights	On time	Avg arrival delay	Cancelled
ONT–SEA	Ontario to Seattle	266	83.1%	0.4 min	0.8%
ONT–DEN	Ontario to Denver	254	72.8%	12.7 min	0.4%
ONT–PHX	Ontario to Phoenix	237	84.0%	4.8 min	0.0%
ONT–DFW	Ontario to Dallas/Fort Worth	213	62.9%	35.4 min	3.8%
ONT–LAS	Ontario to Las Vegas	203	79.8%	5.6 min	1.0%
ONT–SMF	Ontario to Sacramento	178	92.1%	-6.4 min	0.6%
ONT–OAK	Ontario to Oakland	135	90.4%	-2.6 min	0.0%
ONT–SLC	Ontario to Salt Lake City	118	94.1%	-12.5 min	0.8%
ONT–SJC	Ontario to San Jose	110	88.2%	-2.9 min	0.0%
ONT–SFO	Ontario to San Francisco	109	70.6%	17.9 min	0.9%
ONT–ATL	Ontario to Atlanta	82	95.1%	-20.0 min	1.2%
ONT–IAH	Ontario to Houston	40	72.5%	21.6 min	0.0%

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), August 2025.

Delay causes

BTS cause category	Share of delay minutes	National, Aug 2025	Minutes
Air carrier	33.7%	33.1%	9,980
Late-arriving aircraft	42.3%	40.5%	12,543
National Aviation System	19.2%	19.2%	5,706
Extreme weather	4.6%	7.0%	1,365
Security	0.2%	0.1%	64

29,658 delay minutes on 399 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 ONT on time in August 2025?

80.9% of 2,291 scheduled domestic departures left less than 15 minutes late, and 81.4% reached their destination on time. The national figures that month were 76.8% and 76.3%.

How does that compare with a year earlier?

In August 2024, 85.0% of 2,428 departures left on time and 0.9% were cancelled, against 80.9% and 0.8% in August 2025.

Provenance

Source: Bureau of Transportation Statistics, Reporting Carrier On-Time Performance, file for August 2025; public domain. Domestic scheduled flights by reporting carriers, totals and averages only. The site's data runs through July 2026. Full record for ONT · methodology · corrections.