Cheap flights from Ontario to St Louis

One-way fares from $144 · ONT → STL · prices found by travellers in the last 48 hours

Compare all dates St Louis → Ontario
Cheapest fare
$144

Frontier Airlines · Wed, Jan 13

Cheapest month
January

from $144

Direct flights
Not recently

Usually 1+ stop

Quickest trip
4h 23m

2,500 km

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Cheapest month to fly from Ontario to St Louis

Lowest one-way fare per person in each month. Choose a month to see every date.

  1. November 2026 $210
  2. January 2027 Cheapest $144

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Getting around

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About flights from Ontario to St Louis

Ontario (ONT) and St Louis (STL) are about 2,500 km apart. We haven't seen direct fares on this route recently, so expect at least one stop; the quickest journey we've seen takes about 4h 23m. Over the next few months, one-way fares start from $144, and January 2027 is currently the cheapest month to fly.

These prices come from searches travellers made in the last 48 hours, so they move quickly. If you see a good fare, it's worth booking soon. FlightsExp is free to use: you book directly with our travel partner.

Frequently asked questions

How much is a flight from Ontario to St Louis?

The cheapest one-way fare we've seen recently is $144 with Frontier Airlines, departing Wednesday, January 13, 2027. Over the coming months, the lowest fare in each month ranges from $144 to $210.

What is the cheapest month to fly from Ontario to St Louis?

January 2027 currently has the lowest fares, from $144 one way.

Are there direct flights from Ontario to St Louis?

We haven't seen direct fares recently, so most journeys include at least one stop.

How long is the flight from Ontario to St Louis?

The quickest journey we've seen takes about 4h 23m. Ontario and St Louis are around 2,500 km apart.

Which airlines fly from Ontario to St Louis?

Recent fares on this route were with Frontier Airlines.

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