Denver to Ontario in September 2026

Dated one-way fares from Denver to Ontario in September 2026. Use the calendar to see which days are cheaper.

Lowest this month $27

Highest this month $167

Sample fare $27

Airports DEN–ONT

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September 2026 price calendar

From $27 · up to $167

Mon

Tue

Wed

Thu

Fri

Sat

Sun

1 $167 2 $97 3 $97 4 $97 5 $97 6 $97 7 $97 8 $97 9 $27 10 $29 11 $29 12 $29 13 $29 14 $29 15 $31

Ontario ONT

$27

Sep 09, 10:29pm · 2h 18m · 0 stops

DEN → ONT · Frontier Airlines

Ontario ONT

$31

Sep 15, 10:29pm · 2h 18m · 0 stops

DEN → ONT · Frontier Airlines

This page is only September 2026 on the Denver to Ontario route. Open the full route if you want the next months side by side.

Prices move as seats sell. Confirm the live itinerary before you book Denver to Ontario in September 2026.