Submit feedbackComplete travel information for your September journey
Travelers departing Denver International Airport (DEN) for Ontario International Airport (ONT) in September will find shoulder-season pricing and fewer summer crowds. Early September sees a spike around Labor Day, so book flights to avoid the long weekend or secure flexible fares. Nonstop options commonly operated by United and Southwest provide a roughly 2 hour 15 minute to 2 hour 30 minute flight time; check schedules for midweek savings. Pack layers for Denver's autumn-alike mornings and keep an eye on potential wildfire smoke advisories that can impact visibility and operations. For cheap flights DEN to ONT in September, search Tuesday–Thursday departures, set fare alerts, and consider early morning flights to reduce delay risk. Nearby cities served from DEN include Boulder, Colorado Springs, Aurora, and Fort Collins — useful for planning ground transfers and multi-stop trips.
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.
Arriving at Ontario International Airport (ONT) from Denver International Airport (DEN) in September offers pleasant weather and access to Inland Empire attractions with generally lighter summer crowds. Early September sees event-driven traffic due to the Los Angeles County Fair at the Fairplex in Pomona; factor that into ground transportation plans. Nonstop flights from DEN often land mid-morning or evening — plan ground transfers accordingly. For the best experience, pre-book rental cars if visiting Anaheim or Riverside, or use Metrolink for reliable connections into Los Angeles. Keep an eye on regional air quality advisories in September and consider travel insurance that covers weather- or smoke-related disruptions.
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.
Labor Day (early September) often increases demand on routes from Denver International Airport (DEN) to Ontario International Airport (ONT) as families travel. The Los Angeles County Fair at the Fairplex in Pomona typically occurs in September and drives passenger volume through ONT and nearby airports. Anaheim theme parks see lower crowd levels in mid-September, making it a desirable time for families to visit via ONT. Business conferences in downtown Denver and Southern California can also affect weekday seat availability. Plan travel to avoid major event dates or book earlier to secure best fares.
The best time to fly from Denver International Airport (DEN) to Ontario International Airport (ONT) in September is mid-month on Tuesdays through Thursdays, and during early-morning departures when fares and delays tend to be lower. Avoid peak Labor Day weekend if possible, or book well in advance if you must travel during that time. For business travelers, Monday mornings and Friday evenings can be busier and more expensive, while leisure travelers often find bargains midweek.
Nonstop flights from Denver International Airport (DEN) to Ontario International Airport (ONT) save time (about 2 hours 15–30 minutes airborne) and reduce the risk of missed connections, making them ideal for short trips in September. Connecting flights through hubs like Las Vegas (LAS), Phoenix (PHX), or Los Angeles (LAX) can be cheaper but add connection time and potential disruption. If you prioritize price and can accept longer travel time, a one-stop itinerary may be the best value during September fare sales. Business travelers often prefer nonstop routes for reliability, while leisure travelers shop connecting options for cost savings.
United Airlines: Often offers reliable nonstop service from Denver International Airport (DEN) to Ontario International Airport (ONT) with a strong network connection through DEN. Good for loyalty members and business travelers, with standard checked-bag fees depending on fare class. Southwest Airlines: Popular for domestic DEN→ONT travelers due to competitive pricing, two free checked bags, and frequent nonstop or one-stop options in September. Ideal for families and cost-conscious travelers. American Airlines & Alaska Airlines: May offer one-stop itineraries via their respective hubs (PHX, LAX) that can be cheaper but increase travel time; good options when nonstop seats are sold out. Evaluate total price including baggage and seat selection fees when comparing September fares.
Pack layers for variable temperatures: Denver International Airport (DEN) mornings can be cool in September, while Ontario International Airport (ONT) and Southern California days are typically warm. Bring sunscreen and a light jacket; altitude in Denver can cause stronger sun exposure and dehydration, so hydrate before departure. Be aware of potential wildfire smoke that can reduce visibility and affect health — check AirNow and airline advisories the week of travel. For smoother airport experiences, enroll in TSA PreCheck/CLEAR, prepay parking at DEN if driving, and pre-book rental cars or shuttles at ONT for arrivals during busy fair weekends.
Average nonstop flight time from Denver International Airport (DEN) to Ontario International Airport (ONT) is approximately 2 hours 15 minutes to 2 hours 30 minutes, depending on winds and routing. In September, carriers often maintain regular weekday frequencies with possible adjustments around Labor Day. Early-morning departures can reduce the risk of cascading delays, while evening flights may be subject to higher air traffic into Southern California. Check real-time schedules with your airline 24–72 hours before departure for gate and time confirmations.
To find cheap flights from Denver International Airport (DEN) to Ontario International Airport (ONT) in September, monitor fares 3–6 weeks before departure and target midweek travel (Tuesdays–Thursdays). Use fare-tracking tools and set multi-carrier alerts; consider both nonstop and one-stop options through Las Vegas, Phoenix, or Los Angeles for savings. Flying early morning or late evening often reduces fare and delay exposure. Consider low-cost carriers and loyalty program redemptions for discounted tickets. Compare ONT vs LAX pricing — sometimes flying into Ontario International Airport (ONT) yields lower landing fees and better deals for visits to Anaheim or the Inland Empire.