Ontario to San Francisco in December 2026 ONT → SFO
Ontario International Airport (ONT) → San Francisco International Airport (SFO)
For departures in December 2026, the cheapest return found recently is $29 with Frontier Airlines, 5 Dec – 9 Dec, found 4 days ago. The cheapest one-way found recently is $21 with Frontier Airlines, 5 Dec, found today.
Return
We hold return fares on only 1 departure date in December 2026, too few to say what one usually costs.
Cheapest return found recently
$29
5 Dec – 9 Dec · Frontier Airlines
Ontario International Airport (ONT) → San Francisco International Airport (SFO)
out nonstop, back nonstop
found 4 days ago
It is also the cheapest return we hold, of any age.
The cheapest dates in December 2026
| Dates | From | Airline | Stops | Found | |
|---|---|---|---|---|---|
| 5 Dec – 9 Dec | $29 | Frontier Airlines | out nonstop, back nonstop | found 4 days ago | See prices for these dates |
Every date we hold
1 departure date
See every date as a table
| Dates | From | Airline | Airports | Stops | Found | |
|---|---|---|---|---|---|---|
| 5 Dec – 9 Dec | $29 | Frontier Airlines | Ontario International Airport (ONT) → San Francisco International Airport (SFO) | out nonstop, back nonstop | found 4 days ago | See prices for these dates |
Which month looks cheapest?
December 2026 is the cheapest month — from $29.
One-way
In December 2026, the cheapest one-way fare on each of 7 departure dates is usually $35 to $96. Across all 24 departure dates we hold on this route, it is usually $51 to $124. Of the 3 months with enough one-way fares to compare, December 2026 is usually the cheapest.
Cheapest one-way found recently
$21
5 Dec · Frontier Airlines
Ontario International Airport (ONT) → San Francisco International Airport (SFO)
nonstop
found today
It is also the cheapest one-way we hold, of any age.
The cheapest dates in December 2026
| Dates | From | Airline | Stops | Found | |
|---|---|---|---|---|---|
| 5 Dec | $21 | Frontier Airlines | nonstop | found today | Open this trip |
| 24 Dec | $28 | Frontier Airlines | nonstop | found 6 days ago | Open this trip |
| 21 Dec | $42 | Frontier Airlines | nonstop | found 2 days ago | Open this trip |
| 1 Dec | $54 | Frontier Airlines | nonstop | found 5 days ago | Open this trip |
| 23 Dec | $54 | Frontier Airlines | nonstop | found 2 days ago | Open this trip |
Every date we hold
7 departure dates
See the chart as a table
| Dates | From | Airline | Airports | Stops | Found | |
|---|---|---|---|---|---|---|
| 1 Dec | $54 | Frontier Airlines | Ontario International Airport (ONT) → San Francisco International Airport (SFO) | nonstop | found 5 days ago | Open this trip |
| 5 Dec | $21 | Frontier Airlines | Ontario International Airport (ONT) → San Francisco International Airport (SFO) | nonstop | found today | Open this trip |
| 21 Dec | $42 | Frontier Airlines | Ontario International Airport (ONT) → San Francisco International Airport (SFO) | nonstop | found 2 days ago | Open this trip |
| 23 Dec | $54 | Frontier Airlines | Ontario International Airport (ONT) → San Francisco International Airport (SFO) | nonstop | found 2 days ago | Open this trip |
| 24 Dec | $28 | Frontier Airlines | Ontario International Airport (ONT) → San Francisco International Airport (SFO) | nonstop | found 6 days ago | Open this trip |
| 27 Dec | $200 | United Airlines | Ontario International Airport (ONT) → San Francisco International Airport (SFO) | nonstop | found 2 days ago | Open this trip |
| 28 Dec | $138 | Frontier Airlines | Ontario International Airport (ONT) → San Francisco International Airport (SFO) | nonstop | found yesterday | Open this trip |
Which month looks cheapest?
December 2026 is the cheapest month — from $21.
Prices are what travelers' searches on Aviasales found in the last 7 days, in US dollars: the price the seller showed on Aviasales; bags may cost extra. Fares change, so check today's price before you book. How our prices work