OnTimeStats

Historical on-time performance

Ontario to Denver

819 miData through May 2026Source: US DOT · BTS

Flights on ONT–DEN arrive on time 78% of the time over the last 12 months.

On-time rate78%arrived within 15 min
p90 delay45 min1 in 10 flights is worse (tail risk)
Cancelled0.6%of scheduled flights

based on 2,655 flights over the last 12 months. On-time means arriving within 15 minutes (BTS standard).

By airline

How each carrier compares

  • United Airlinesbest
    On-time83%
    Medianon time
    p9040 min
    Cancel0.6%
    Flights867
  • Frontier Airlines
    On-time76%
    Medianon time
    p9070 min
    Cancel1.0%
    Flights519
  • Southwest Airlines
    On-time76%
    Medianon time
    p9040 min
    Cancel0.4%
    Flights1,269

Why flights run late

Delay causes

  • Airline20%
  • Weather2%
  • Air traffic (NAS)38%
  • Late aircraft40%
  • Security0%

Most delay minutes here are attributed to Late aircraft.

When flights don't go

Why flights were cancelled

  • Airline80%
  • Weather7%
  • Air traffic (NAS)13%
  • Security0%

Most cancellations here are attributed to Airline. Shares are among 15 cancellations with a reported cause (BTS reports causes from June 2003).

Over time

On-time trend

By season

On-time rate by month

When to fly

Best time to fly ONT → DEN

All airlines · rolling 36 months (2023-06 .. 2026-05).

Best time of day

Mornings are the most reliable time of day to fly this route — 92% on time.

  • Mornings92% on time · p90 5 min · 3,622 flights
  • Early mornings79% on time · p90 40 min · 417 flights
  • Middays77% on time · p90 45 min · 2,235 flights
  • Overnights74% on time · p90 60 min · 204 flights
  • Evenings71% on time · p90 75 min · 822 flights
  • Afternoons65% on time · p90 70 min · 1,087 flights

Best day of week

Saturdays are the most reliable day to fly this route — 86% on time.

  • Saturdays86% on time · p90 20 min · 1,052 flights
  • Tuesdays82% on time · p90 30 min · 1,155 flights
  • Wednesdays82% on time · p90 35 min · 1,156 flights
  • Sundays80% on time · p90 35 min · 1,222 flights
  • Thursdays80% on time · p90 40 min · 1,261 flights
  • Fridays80% on time · p90 40 min · 1,278 flights
  • Mondays80% on time · p90 40 min · 1,263 flights

Keep exploring

Related pages

Delay predictorfor this route→ONT airportOntario→DEN airportDenver→Southwest Airlinesairline profile→United Airlinesairline profile→Frontier Airlinesairline profile→Seasonal delay patternsguide→

Methodology

A flight is on time when it arrives within 15 minutes of schedule — the US DOT / BTS standard. Median and p90(the “1-in-10 bad day”) are read from the full arrival-delay distribution, never averaged across periods.

Figures cover a carrier’s own BTS-coded flights. Cells below ~200 flights are flagged as limited data. All numbers are pre-computed from public BTS On-Time Performance data.