Route profile
SEA→ONT
Flight reliability, delays and best times to fly from Seattle to Ontario. · 956 miles
Right now
Current conditions at both ends of this route.
Aviation weather is not currently a factor. FAA operational data — ground stops, ground delay programs and closures — is not currently available to FlyerIntel.
Aviation weather is not currently a factor. FAA operational data — ground stops, ground delay programs and closures — is not currently available to FlyerIntel.
Airport conditions describe the airfield, not any individual flight. An airport operating normally is not a guarantee that a specific flight will depart on time.
Route reliability
July 2023 – June 2026
Better than 83% of comparable major US routes (4,577 compared)
Calculated from 7,500 flights. How this is calculated
Source: US DOT Bureau of Transportation Statistics · Data covering July 2023 – June 2026
Best time to fly
On-time arrival rate by scheduled local departure time.
SEA → ONT flights departing 5–9 AM arrived on time 90.5% of the time, against 66.5% for 9 PM–5 AM departures — a gap of 24.0 percentage points.
By departure window
By departure hour
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – June 2026 · Buckets with fewer than 120 flights are not scored.
Airlines on this route
Performance by the carrier that actually operated the flight.
| Carrier | Flights | On time | Cancelled | Median delay | Severe |
|---|---|---|---|---|---|
| Alaska Airlines | 3,718 | 77.0% | 1.53% | -2 min | 4.5% |
| SkyWest Airlines | 2,805 | 89.6% | 0.14% | -8 min | 2.3% |
| Delta Air Lines | 514 | 85.1% | 0.97% | -11 min | 6.5% |
| Frontier Airlines | 463 | 77.4% | 2.16% | -6 min | 8.8% |
SkyWest Airlines arrived on time 12.6 percentage points more often than Alaska Airlines on this route.
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – June 2026 · Carriers with fewer than 200 flights on this route are not listed.
Other ways to fly Seattle to Los Angeles
Airport pairs serving the same journey, grouped by the DOT's own city-market definition. They do not perform the same way.
SEA → SNA is the most reliable pairing for this journey at 85.6% on time, against 77.3% for SEA → BUR.
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – June 2026 · Grouped by DOT city market, which places Newark with the New York airports and Baltimore with the Washington ones.
Individual flights on this route
The same route is not equally reliable at every hour. These are the flight numbers with enough operating history to judge separately.
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – June 2026 · Flight numbers with fewer than 270 operations on this route, or no longer scheduled, are not listed.
Weekly and seasonal patterns
By day of week
Tuesday is historically the most reliable day and Sunday the least, a gap of 7.3 percentage points.
By month
August is historically the weakest month and October the strongest, a spread of 10.6 percentage points.
Historical trend
On-time arrival rate by month.
Over the most recent 12 months (2025-07 to 2026-06), on-time arrivals averaged 82.9% against 83.4% in the 12 months before — broadly unchanged.
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – June 2026
Data and methodology
All figures on this page are calculated by FlyerIntel from 7,500 SEA → ONT flight records published by the US DOT Bureau of Transportation Statistics, covering July 2023 – June 2026. A flight is counted as delayed when it arrives 15 or more minutes after its scheduled arrival time, following BTS methodology. Cancelled and diverted flights have no arrival time and are excluded from on-time rates rather than counted as late.