Ontario International in December 2025

78.8%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 December 2025, reporting carriers scheduled 2,132 domestic departures from Ontario International (ONT). 78.8% left less than 15 minutes late and 81.7% reached their destination on time; 0.7% were cancelled.

Nationally that month, 72.0% of flights departed on time and 71.9% arrived on time, so ONT departures were 6.8 points above the national departure figure.

A year earlier, in December 2024, the airport had 2,116 departures with 84.4% leaving on time: a change of −5.6 points, with flights up 1%.

Flights arriving at ONT that month were on time 74.3% of the time (2,132 scheduled arrivals).

Of the delay minutes that carriers assigned to a BTS cause category that month, late-arriving aircraft 46%, air carrier 37% and national aviation system 15%.

On time 81.7%
Arrived 15+ minutes late 17.5%
Cancelled 0.7%
Diverted 0.1%

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

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

Measure	Dec 2025	Dec 2024	ONT, 12 months to Jul 2026	All reported flights, Dec 2025
Departed on time	78.8%	84.4%	80.3%	72.0%
Arrived on time	81.7%	84.7%	81.2%	71.9%
Cancelled	0.7%	0.3%	0.9%	1.5%
Average departure delay (late minutes only)	14.8 min	11.5 min	13.7 min	21.2 min
Scheduled departures a day	71	71	71	19,410
Scheduled departures	2,132	2,116	25,854	582,304

Airlines that month

Reporting carrier	Flights	Share	On time	Avg arrival delay	Cancelled
WN Southwest Airlines	1,005	47%	81.8%	2.6 min	0.3%
AA American Airlines	336	16%	81.8%	13.9 min	0.0%
UA United Airlines	171	8%	81.9%	9.8 min	0.0%
AS Alaska Airlines	169	8%	84.0%	-0.8 min	1.2%
F9 Frontier Airlines	157	7%	73.9%	16.8 min	3.2%
DL Delta Air Lines	147	7%	85.7%	1.0 min	2.7%
OO SkyWest Airlines	147	7%	82.3%	0.6 min	0.7%

Busiest routes that month

Route	Cities	Flights	On time	Avg arrival delay	Cancelled
ONT–PHX	Ontario to Phoenix	282	80.1%	8.9 min	0.0%
ONT–LAS	Ontario to Las Vegas	206	83.5%	8.1 min	1.0%
ONT–DFW	Ontario to Dallas/Fort Worth	201	80.6%	14.1 min	1.5%
ONT–SEA	Ontario to Seattle	200	80.5%	3.1 min	1.0%
ONT–DEN	Ontario to Denver	195	76.9%	11.5 min	0.0%
ONT–SMF	Ontario to Sacramento	179	85.5%	0.4 min	0.0%
ONT–OAK	Ontario to Oakland	121	79.3%	2.8 min	0.0%
ONT–SJC	Ontario to San Jose	118	89.8%	-6.0 min	0.8%
ONT–SFO	Ontario to San Francisco	104	74.0%	10.2 min	1.9%
ONT–SLC	Ontario to Salt Lake City	90	85.6%	1.8 min	0.0%
ONT–ATL	Ontario to Atlanta	88	85.2%	0.0 min	4.5%
ONT–IAH	Ontario to Houston	44	77.3%	6.0 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), December 2025.

Delay causes

BTS cause category	Share of delay minutes	National, Dec 2025	Minutes
Air carrier	36.6%	33.3%	9,595
Late-arriving aircraft	46.4%	41.1%	12,180
National Aviation System	15.0%	19.1%	3,941
Extreme weather	1.6%	6.4%	414
Security	0.4%	0.2%	95

26,225 delay minutes on 373 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 December 2025?

78.8% of 2,132 scheduled domestic departures left less than 15 minutes late, and 81.7% reached their destination on time. The national figures that month were 72.0% and 71.9%.

How does that compare with a year earlier?

In December 2024, 84.4% of 2,116 departures left on time and 0.3% were cancelled, against 78.8% and 0.7% in December 2025.

Provenance

Source: Bureau of Transportation Statistics, Reporting Carrier On-Time Performance, file for December 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.