Ontario International Airport has put forward an expansion proposal that centers on a new passenger terminal and a six-story parking garage, according to a report by the Inland Valley Daily Bulletin.

The proposal marks the most significant physical growth plan for the Southern California airport since it reverted to local ownership from Los Angeles World Airports in 2016. Details released so far identify two headline elements: additional terminal capacity and a major structured parking structure.

What does the proposal contain?

The plan, as outlined by the Daily Bulletin, comprises:

• A new terminal building to add passenger processing capacity beyond the airport's existing two terminals
• A six-story parking garage to expand on-airport parking inventory

The airport authority has not yet published a full breakdown of costs, construction timelines or phased delivery dates in the material reported. Those figures will determine whether the project proceeds on a schedule consistent with recent traffic growth at the inland gateway.

Why does the capacity matter?

Ontario has positioned itself as a reliever airport for constrained airspace and gate availability across the Los Angeles basin. Terminal and parking capacity directly constrain an airport's ability to attract additional airline commitments: carriers weigh gate availability, processing throughput and passenger amenities when allocating aircraft to a station.

A new terminal would give Ontario room to add departures without reworking existing facilities during construction. A structured garage increases the share of passengers using on-airport parking, a revenue line that funds capital programs at most US mid-size airports.

What happens next?

The proposal now moves through the airport authority's planning and approval process. Environmental review, board votes and airline consultation typically precede groundbreaking on projects of this scale at California public airports, and each step can shift the delivery timeline.

Until the authority publishes cost estimates and construction phasing, the expansion remains a proposal rather than a committed capital program — the distinction that separates planned capacity from capacity an airline can schedule against.

The next milestone to watch is the Ontario International Airport Authority's formal consideration of the plan, where budgets and dates would attach to the terminal and garage concepts now on the table.