Ontario International in April 2026

80.7%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 April 2026, reporting carriers scheduled 2,119 domestic departures from Ontario International (ONT). 80.7% left less than 15 minutes late and 82.4% reached their destination on time; 0.3% were cancelled.

Nationally that month, 79.1% of flights departed on time and 78.9% arrived on time, so ONT departures were 1.6 points above the national departure figure.

A year earlier, in April 2025, the airport had 2,250 departures with 86.1% leaving on time: a change of −5.4 points, with flights down 6%.

Flights arriving at ONT that month were on time 79.2% of the time (2,119 scheduled arrivals).

Of the delay minutes that carriers assigned to a BTS cause category that month, late-arriving aircraft 41%, air carrier 35% and national aviation system 23%.

On time 82.4%
Arrived 15+ minutes late 17.1%
Cancelled 0.3%
Diverted 0.2%

Every scheduled departure from ONT in April 2026, judged by arrival at the destination.

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

Measure	Apr 2026	Apr 2025	ONT, 12 months to Jul 2026	All reported flights, Apr 2026
Departed on time	80.7%	86.1%	80.3%	79.1%
Arrived on time	82.4%	85.3%	81.2%	78.9%
Cancelled	0.3%	0.4%	0.9%	0.9%
Average departure delay (late minutes only)	12.4 min	10.1 min	13.7 min	14.5 min
Scheduled departures a day	71	75	71	19,931
Scheduled departures	2,119	2,250	25,854	597,919

Airlines that month

Reporting carrier	Flights	Share	On time	Avg arrival delay	Cancelled
WN Southwest Airlines	972	46%	79.6%	1.2 min	0.1%
AA American Airlines	270	13%	86.3%	4.8 min	0.7%
UA United Airlines	228	11%	76.8%	6.6 min	0.4%
OO SkyWest Airlines	176	8%	93.8%	-11.4 min	0.0%
F9 Frontier Airlines	160	8%	73.8%	11.1 min	0.0%
AS Alaska Airlines	152	7%	86.8%	-7.2 min	1.3%
DL Delta Air Lines	137	6%	92.0%	-1.2 min	0.0%
MQ Envoy Air	24	1%	95.8%	-7.9 min	0.0%

Busiest routes that month

Route	Cities	Flights	On time	Avg arrival delay	Cancelled
ONT–PHX	Ontario to Phoenix	252	86.9%	2.4 min	0.0%
ONT–DEN	Ontario to Denver	205	85.9%	-1.6 min	0.0%
ONT–LAS	Ontario to Las Vegas	202	71.8%	9.7 min	0.0%
ONT–SEA	Ontario to Seattle	200	90.5%	-10.4 min	0.5%
ONT–SMF	Ontario to Sacramento	184	82.6%	-1.1 min	0.5%
ONT–DFW	Ontario to Dallas/Fort Worth	180	87.2%	4.0 min	1.1%
ONT–SFO	Ontario to San Francisco	124	53.2%	23.4 min	0.0%
ONT–OAK	Ontario to Oakland	116	85.3%	-2.0 min	0.0%
ONT–SJC	Ontario to San Jose	106	84.0%	-1.9 min	0.0%
ONT–SLC	Ontario to Salt Lake City	99	90.9%	-9.9 min	0.0%
ONT–ATL	Ontario to Atlanta	77	90.9%	6.5 min	0.0%
ONT–IAH	Ontario to Houston	39	94.9%	-5.4 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), April 2026.

Delay causes

BTS cause category	Share of delay minutes	National, Apr 2026	Minutes
Air carrier	34.9%	33.5%	7,755
Late-arriving aircraft	41.3%	40.4%	9,166
National Aviation System	22.7%	21.0%	5,037
Extreme weather	1.0%	5.0%	227
Security	0.1%	0.1%	14

22,199 delay minutes on 363 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 April 2026?

80.7% of 2,119 scheduled domestic departures left less than 15 minutes late, and 82.4% reached their destination on time. The national figures that month were 79.1% and 78.9%.

How does that compare with a year earlier?

In April 2025, 86.1% of 2,250 departures left on time and 0.4% were cancelled, against 80.7% and 0.3% in April 2026.

Provenance

Source: Bureau of Transportation Statistics, Reporting Carrier On-Time Performance, file for April 2026; 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.