✈️ Flight Guide: Denver (DEN) → Ontario (ONT)

For a domestic flight from Denver International Airport (DEN) to Ontario International Airport (ONT) in September, arrive at least 90 minutes before departure if you have checked bags, and 60 minutes for carry-on only. September can include busy holiday-adjacent travel (Labor Day early in the month), so add extra buffer during peak mornings and evenings. Use TSA PreCheck or CLEAR to shorten the security wait.

Yes — multiple carriers typically operate nonstop services between Denver International Airport (DEN) and Ontario International Airport (ONT) in September, especially United Airlines and Southwest Airlines on many days. Nonstop frequency can vary mid-week and around holiday weekends, so check carrier schedules for the exact September dates you plan to travel. Booking earlier in the month often secures more nonstop options and better fares.

In September, fares from Denver International Airport (DEN) to Ontario International Airport (ONT) often drop compared to summer peak months — typical round-trip fares can range from budget deals around $120–$250 to higher prices during holiday weekends. Booking 21–45 days ahead and flying midweek usually yields the best September pricing. Use fare alerts on Google Flights or sign up for airline newsletters to capture limited-time cheap flights DEN to ONT deals.

Denver International Airport (DEN) has extensive ground transport including RTD A-line train to downtown Denver, ride-hailing, shuttles, and long-term parking options that make connecting to your terminal straightforward for flights to Ontario International Airport (ONT). If you’re traveling from nearby cities like Boulder, Colorado Springs, Aurora, or Fort Collins, consider airport shuttle services or car rentals for flexible scheduling in September. Book parking or shuttles in advance for holiday weekends.

September is generally a stable travel month, but occasional late-summer weather such as thunderstorms or smoky conditions from regional wildfires can affect flights departing Denver International Airport (DEN). Airlines may issue delays or advisories, so check real-time flight status through the airline or the DEN website the morning of travel. Purchase refundable or flexible tickets if your plans are sensitive to weather-related disruptions.

From Denver International Airport (DEN) you can easily access Denver, Boulder, Colorado Springs, Fort Collins, and Aurora as part of multi-city itineraries that include Ontario International Airport (ONT). If you plan a California stopover, combine ONT with Los Angeles, Anaheim (Disneyland), Riverside, or Pomona for inland Southern California attractions. Use multi-city search tools to find optimized routing and cheap flights DEN to ONT with convenient connections in September.

Ontario International Airport (ONT) offers taxis, ride-sharing pickup zones, airport shuttles, rental cars, and Metrolink/Omnitrans connections to the Inland Empire. In September, traffic is usually moderate compared with summer peak travel, but expect increased demand during events like the Los Angeles County Fair; pre-book shuttles or rental cars when possible. Consider ride-hailing apps or the ONT Courtesy Van for quick terminal-to-rental car transfers.

Travel time from Ontario International Airport (ONT) to downtown Los Angeles typically ranges from 45 minutes to 90 minutes depending on time of day and traffic; morning arrivals from Denver International Airport (DEN) in September often avoid peak rush hour if scheduled early. Always check real-time traffic apps, and consider Metrolink weekday schedules for a predictable alternative to driving. Plan extra time for event traffic during fair weekends in Pomona.

For domestic flights from Denver International Airport (DEN) to Ontario International Airport (ONT), baggage claim is straightforward — follow ground transportation signage after collecting bags. There are no customs procedures for a domestic arrival. If you connect to an international flight beyond ONT, confirm baggage routing with your airline; otherwise, expect quick pickup and short walks to rental car or rideshare areas.

Ontario International Airport (ONT) is a gateway to Los Angeles, Pomona, Riverside, Anaheim (Disneyland), and San Bernardino. September is a great month to visit theme parks with lower crowds and to catch regional events like the Los Angeles County Fair in Pomona. For day trips, consider Pasadena, Long Beach, or Orange County depending on your itinerary and transportation choices.

Southern California can experience intermittent wildfire smoke in late summer and early fall that affects visibility and air quality; this occasionally impacts flights into Ontario International Airport (ONT) in September. Airlines may delay or re-route flights during severe smoke events. Monitor airline notifications and local air quality reports before traveling; bring masks if you have respiratory sensitivities and check refundable or flexible ticket options.

To find cheap flights to Ontario International Airport (ONT) from Denver International Airport (DEN) in September, compare fares across airlines, set price alerts, and search for Tuesday–Thursday departures. Consider nonstop flights for time savings or one-stop options through Las Vegas or Phoenix for lower prices. Use fare tools like Google Flights and sign up for airline promos to capture limited-time DEN to ONT deals.