Airport month record

ONTAPR

Ontario International in April 2026

Departures: 2,119
Month: April 2026
National, same month: 79.8%
Carriers: 7

Historical statistics for April 2026, not live status or a forecast for this year’s April. For today’s conditions at ONT, see live FAA status.

ONT in April lands a B+, 3 points better than the national rate of 79.8%. About one flight in six arrives 15 minutes late or worse, and those flights are late by about an hour on average. That rests on 2,119 flights, with a median arrival 9 minutes early.

On time

82.8%

Arrivals under 15 minutes late, of 2,109 completed departures

Avg delay

61 min

Across delayed arrivals only, not all flights

Cancelled

0.28%

Nationally in April: 0.90%

Whole year

81.9%

ONT across all twelve months

These figures cover 2,119 departures from Ontario International in April 2026. 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

April next to ONT's other months

Against ONT's own year, April ran level with the twelve-month rate of 81.9%, which makes it number five of twelve months, best first. Cancellations were unusually low for ONT in April, at 0.28% against 0.87% across the year. Either side of it, March ran 82.8% on time and May 80.0%, so this month sits in line with its neighbours.

ONT month by month
Month	Flights	On time	Avg delay	Cancelled	Grade
September 2025	2,177	84.8%	76 min	0.51%	B+
October 2025	2,265	81.6%	64 min	0.49%	B+
November 2025	2,184	81.9%	63 min	2.06%	B
December 2025	2,132	82.4%	70 min	0.70%	B+
January 2026	1,892	86.5%	87 min	1.69%	A
February 2026	1,734	87.8%	70 min	0.35%	A+
March 2026	2,081	82.8%	57 min	1.01%	B
April 2026 (this page)	2,119	82.8%	61 min	0.28%	B+
May 2026	2,298	80.0%	58 min	0.70%	B+
June 2026	2,304	76.7%	66 min	1.00%	B
July 2026	2,377	77.9%	75 min	0.88%	B+
August 2026	2,228	80.9%	70 min	0.81%	B+

Departure window

The best time of day to leave ONT in April

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 22 points, against half a point between the best and worst carrier.

5am–8am554 flights94.7%
8am–11am284 flights85.5%
11am–2pm445 flights79.7%
2pm–5pm265 flights72.3%
5pm–8pm296 flights75.0%
8pm–5am275 flights79.5%

Scale runs 65% to 100%.

Book the early departure. Flights leaving between 5am–8am arrive on time 94.7% of the time, against 72.3% for the afternoon window. That is 22 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 5am–8am window is the busiest, with 554 flights scheduled in it.

Across the week, Tuesday is the strongest day at 89.6% on time and Thursday the weakest at 77.1%, a spread of 13 points.

Carrier by carrier

Which airlines ran best at ONT in April

Only one carrier clears this site's 365-flight floor here, so there is no comparison to draw. The table below is the full picture.

Carriers at ONT in April 2026
Airline	Flights	On time	Avg delay	Cancelled	Grade
Southwest Airlines	972	79.9%	42 min	0.10%	B+
American Airlinesthin sample	270	87.3%	142 min	0.74%	A+
United Airlinesthin sample	228	77.1%	64 min	0.44%	B+
SkyWest Airlinesthin sample	176	93.8%	48 min	0.00%	A+
Frontier Airlinesthin sample	160	73.8%	79 min	0.00%	C+
Alaska Airlinesthin sample	152	88.0%	41 min	1.32%	A
Delta Air Linesthin sample	137	92.6%	130 min	0.00%	A+

Route by route

Busiest routes out of ONT in April

Routes from ONT in April 2026
Route	Flights	On time	Avg delay	Cancelled	Grade
ONT to PHX · Phoenixthin sample	252	86.9%	80 min	0.00%	A+
ONT to DEN · Denverthin sample	205	86.3%	63 min	0.00%	A+
ONT to LAS · Las Vegasthin sample	202	71.8%	57 min	0.00%	C+
ONT to SEA · Seattlethin sample	200	91.0%	50 min	0.50%	A+
ONT to SMF · Sacramentothin sample	184	83.1%	47 min	0.54%	B+
ONT to DFW · Dallas-Fort Worththin sample	180	88.2%	163 min	1.11%	A
ONT to SFO · San Franciscothin sample	124	53.2%	58 min	0.00%	F+
ONT to OAK · Oaklandthin sample	116	85.3%	59 min	0.00%	A+
ONT to SJC · San Josethin sample	106	84.0%	40 min	0.00%	B+
ONT to SLC · Salt Lake Citythin sample	99	91.8%	38 min	0.00%	A+
ONT to ATL · Atlantathin sample	77	90.9%	167 min	0.00%	A+
ONT to IAH · Houstonthin sample	39	94.9%	44 min	0.00%	A+
ONT to PDX · Portlandthin sample	35	94.1%	38 min	2.86%	A
ONT to DAL · Dallasthin sample	33	66.7%	28 min	0.00%	C+
ONT to HNL · Honoluluthin sample	30	83.3%	23 min	0.00%	B+
ONT to BNA · Nashvillethin sample	30	66.7%	39 min	0.00%	C+
ONT to BWI · Baltimorethin sample	30	93.3%	26 min	0.00%	A+
ONT to HOU · Houstonthin sample	30	40.0%	29 min	0.00%	F+
ONT to MDW · Chicagothin sample	30	82.8%	38 min	0.00%	B+
ONT to CLT · Charlottethin sample	30	93.1%	22 min	0.00%	A+
ONT to ORD · Chicagothin sample	30	82.8%	65 min	3.33%	B−
ONT to STS · Santa Rosathin sample	30	93.3%	42 min	0.00%	A+

Delay causes

What held ONT up in April

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 22,000 reported delay minutes.

Late-arriving aircraft
41%
Carrier
35%
National Airspace System
23%
Extreme weather
1%
Security
0%

41% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 22,000 reported delay minutes here, that single category outweighs weather by 40 to one. The split is drawn from 22,199 reported delay minutes.

Cancellations are rare at 0.28%, below the national 0.90% 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.

Badly late arrivals are rare here: only 4.4% land an hour or more behind schedule, against 6.4% nationally. Connections built on this flight are about as safe as US domestic connections get, though a cancelled flight still ignores every layover you give it.

What to do with this

Flying from ONT in April

For a April trip through ONT: expect 82.8% on time and 0.28% cancelled, going by April 2026. The 5am–8am window was the strongest part of the day.

Ontario International (ONT), the whole year
ONT in September84.8%
ONT in October81.6%
ONT in November81.9%
ONT in December82.4%
ONT in January86.5%
ONT in February87.8%
ONT in March82.8%
ONT in May80.0%
ONT in June76.7%
ONT in July77.9%
ONT in August80.9%

Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated 22 October 2026; recomputed monthly. How this data is collected.

Key figures