Route profile
ATL→ONT
Flight reliability, delays and best times to fly from Atlanta to Ontario, 1,900 miles.
Right now
Aviation weather is not currently a factor.
Aviation weather is not currently a factor.
Route reliability
July 2023 – July 2026
Better than 45% of comparable major US routes (4,598 compared)
Calculated from 2,919 flights. How this is calculated
ATL → ONT arrives on time 76.3% of the time; the return trip, ONT → ATL, arrives on time 91.1% of the time, a 14.8-point gap between the two directions of the same city pair.
ATL → ONT spends 22.4 minutes on the ground on a 1,900-mile trip: 16.9 minutes from pushback to wheels-up at ATL and 5.5 minutes from touchdown to gate at ONT.
Source: US DOT Bureau of Transportation Statistics · Data covering July 2023 – July 2026
What stands out
Reliability here swings unusually widely by season, a wider month-to-month spread than 93% of 3,357 comparable routes.
89.1% on time in a typical October, against 63.9% in July.
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – July 2026 · Ranked against every other route with the same kind of figure and at least 3,357 in the comparison.
What sets this route apart
Where ATL to ONT differs most from similar routes by hour, weekday, month and airline, July 2023 – July 2026.
ATL to ONT is at its best against routes of similar length for flights scheduled at 7 PM: 78.1% arrive on time, 10.9 points ahead of the 67.2% those routes manage at that hour. Against all other routes the gap is 10.3 points.
ATL to ONT struggles most at 9 PM: 65.8% of its flights scheduled then arrive on time, 6.7 points behind the 72.5% on routes of similar length at the same hour.
In May, ATL to ONT runs 10.3 points below routes of similar length, 65.7% on time to 76.0%. Against all other routes the gap is 9.6 points.
October is kinder to ATL to ONT than to routes of similar length: 89.1% on time against 83.7%, 5.4 points better. Against all other routes the gap is 6.1 points.
Delta Air Lines’ flights on ATL to ONT arrive on time 76.9% of the time, 4.7 points below the 81.6% it manages on its routes of similar length. Against all other routes the gap is 4.6 points.
ATL to ONT against comparable routes
July 2023 – July 2026| Measure | This route | Compared with | Them | Gap | Flights behind it |
|---|---|---|---|---|---|
| Hour: 7 PM departures | 78.1% | routes of similar length | 67.2% | +10.9 pts | 137 here, 44,068 there |
| Hour: 9 PM departures | 65.8% | routes of similar length | 72.5% | −6.7 pts | 442 here, 31,973 there |
| Month: May | 65.7% | routes of similar length | 76.0% | −10.3 pts | 251 here, 100,134 there |
| Month: October | 89.1% | routes of similar length | 83.7% | +5.4 pts | 247 here, 96,796 there |
| Airline: Delta Air Lines | 76.9% | routes of similar length | 81.6% | −4.7 pts | 2,809 here, 299,180 there |
Each comparison pools the flights of other routes, with this route’s own left out. Similar length means within 15% of this route’s 1,900 miles, with at least 5 such routes. A bucket is set against the most comparable group that has enough flights: similar length, then the same origin (at least 3 routes), then all other routes. Hours, weekdays and months appear only where both sides have 120 completed flights, and airlines where both have 600. The gap must be at least 2 points and 2 standard errors, and only the largest gap each way is kept per measure. These are differences in the flights counted, not causes.
When it goes wrong
July 2023 – July 2026
45 min late
against a median of 3 min early
Percentiles over 2,919 operations; cancelled and diverted flights are counted separately.
Will your connection be tight enough?
Layovers at ONT after arriving from ATL.
| Connection time | Chance of missing | Reads as |
|---|---|---|
| 30 min | 42% | Likely to miss |
| 45 min | 23% | High risk |
| 60 min | 14% | Some risk |
| 90 min | 7.0% | Some risk |
| 120 min | 3.7% | Low risk |
This is one leg of a connection. Gate changes and the next flight's own schedule matter too. And a connection can fail before delay is even the question — this route cancels 1.37% of the time and diverts 0.21% of the time, which a late arrival never shows up in.
Chance of missing is the share of 2,873 arrivals on this route that landed later than the connection time less 30 minutes to reach the next gate.
The worst tenth of arrivals on this route land at least 45 minutes late (90th-percentile gate arrival delay), over 2,919 operations.
Any other layover length: connection checker.
Best time to fly
ATL → ONT flights departing 5–9 AM arrived on time 92.5% of the time, against 65.6% for 9 PM–5 AM departures, a gap of 26.9 percentage points.
By departure window
By departure hour
- 12 AM to 7 AM: too few flights to score
- 8 AM: 92.5% on time from 234 flights
- 9 AM: 85.5% on time from 787 flights
- 10 AM: 77.4% on time from 140 flights
- 11 AM to 4 PM: too few flights to score
- 5 PM: 76.4% on time from 351 flights
- 6 PM: 66.3% on time from 255 flights
- 7 PM: 78.1% on time from 138 flights
- 8 PM: 70.9% on time from 437 flights
- 9 PM: 65.8% on time from 449 flights
- 10 PM to 11 PM: too few flights to score
Departure windows with fewer than 120 flights are not scored.
Why ATL → ONT runs late
July 2023 – July 2026
crew, maintenance, boarding and fueling, all within the carrier’s control
the inbound aircraft was late, so this flight started late
airspace and airport capacity, including weather-driven flow control
weather severe enough to stop this flight specifically
screening or terminal security incidents
Share of the delay minutes US DOT attributed to each cause for ATL → ONT. Only delays of 15 minutes or more are attributed.
Airlines on this route
Carriers with at least 200 flights, by the airline that operated each one.
| Carrier | Flights | On time | Cancelled | Median delay | Severe |
|---|---|---|---|---|---|
| Delta Air Lines | 2,852 | 76.9% | 1.30% | -4 min | 6.9% |
Other ways to fly Atlanta to Los Angeles
Airport pairs in the same two city markets, as the DOT defines them.
| Route | Flights | On time | Cancelled | Median delay | Score |
|---|---|---|---|---|---|
| ATL→LAX Atlanta to Los Angeles | 16,302 | 77.0% | 0.85% | -4 min | 67 |
| ATL→ONT this route Atlanta to Ontario | 2,919 | 76.3% | 1.37% | -3 min | 64 |
Flights on this route
Flight numbers with at least 600 operations here and still on the schedule.
Weekly and seasonal patterns
By day of week
Wednesday is historically the most reliable day and Sunday the least, a gap of 8.1 percentage points.
By month
- Jan: 78.8%
- Feb: 78.1%
- Mar: 84.1%
- Apr: 74.9%
- May: 65.7%
- Jun: 70.9%
- Jul: 63.9%
- Aug: 70.9%
- Sep: 83.3%
- Oct: 89.1%
- Nov: 83.5%
- Dec: 83.3%
July is historically the weakest month and October the strongest, a spread of 25.2 percentage points.
Reliability over time
July 2023 – July 2026
- July 2023: too few flights to score (118)
- August 2023: 61.2% from 121 flights
- September 2023: too few flights to score (82)
- October 2023: too few flights to score (78)
- November 2023: too few flights to score (72)
- December 2023: too few flights to score (80)
- January 2024: too few flights to score (63)
- February 2024: too few flights to score (58)
- March 2024: too few flights to score (62)
- April 2024: too few flights to score (72)
- May 2024: too few flights to score (79)
- June 2024: too few flights to score (87)
- July 2024: too few flights to score (82)
- August 2024: too few flights to score (85)
- September 2024: too few flights to score (80)
- October 2024: too few flights to score (84)
- November 2024: too few flights to score (77)
- December 2024: too few flights to score (88)
- January 2025: too few flights to score (66)
- February 2025: too few flights to score (56)
- March 2025: too few flights to score (62)
- April 2025: too few flights to score (77)
- May 2025: too few flights to score (81)
- June 2025: too few flights to score (84)
- July 2025: too few flights to score (88)
- August 2025: too few flights to score (82)
- September 2025: too few flights to score (77)
- October 2025: too few flights to score (85)
- November 2025: too few flights to score (84)
- December 2025: too few flights to score (88)
- January 2026: too few flights to score (64)
- February 2026: too few flights to score (56)
- March 2026: too few flights to score (62)
- April 2026: too few flights to score (78)
- May 2026: too few flights to score (93)
- June 2026: too few flights to score (80)
- July 2026: too few flights to score (88)
Over the most recent 12 months (2025-08 to 2026-07), on-time arrivals averaged 75.3% against 77.3% in the 12 months before — declining by 2.0 percentage points.
Data and methodology
Calculated by FlyerIntel from 2,919 ATL → ONT flight records from the US DOT Bureau of Transportation Statistics, covering July 2023 – July 2026. Late means 15 or more minutes past scheduled arrival; cancelled and diverted flights are left out of on-time rates.
Full methodology · Data sources · Report a problem
Related research: How Long a Layover Needs to Be · Two Airlines on One Route · Best Time of Day to Fly From Major US Airports
Analysis last recomputed