Flight Check

Best Airline: ONT to DEN

Ontario to Denver — airline reliability comparison

United Airlines is the most reliable airline on the ONT to DEN route with a 86% on-time rate, compared to Frontier Airlines at 81%. Based on 2,955 flights tracked.

This route involves weather-prone airports and high-congestion airports, which can affect reliability regardless of airline.

Source: Bureau of Transportation Statistics. Updated October 2026.

On-Time Rate by Airline

United Airlines86%
Southwest Airlines83%
Frontier Airlines81%

ONT to DEN Airline Comparison

AirlineOn-Time %Cancel %Avg DelayFlights
United AirlinesUABest86%0.6%82m2,955
Southwest AirlinesWN83%0.7%58m4,701
Frontier AirlinesF9Worst81%1.2%88m2,275

Route Overview

83%
Overall On-Time
69m
Avg Delay
0.8%
Cancel Rate
9,938
Total Flights
ONT to DEN Route DetailsReturn: DEN to ONT
ONT AirportDEN Airport

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Data last updated October 2026. Source: Bureau of Transportation Statistics.