ONTARIO, Calif. -

Without millions of dollars in investments, L.A./Ontario International Airport could face further desertion by airlines and passengers, according to a report released today by Inland Empire officials pushing for local control of the facility.

The report concludes the Ontario airport will continue on a ``downward spiral'' that could bring passenger levels under 2 million by between 2020 and 2024, and result in the loss of $430 million in economic activity a year.

The study, conducted by aviation consulting firm Oliver Wyman of Washington, D.C., was commissioned by the Ontario International Airport Authority, a coalition of government officials who want control of the airport.

L.A./Ontario is operated by Los Angeles World Airports, a Los Angeles city agency that also runs Los Angeles International Airport and Van Nuys Airport.

The report comes as negotiation talks with Los Angeles have stalled, with Inland Empire officials balking at Los Angeles' asking price of $475 million for giving up the airport. Ontario-area officials were only willing to pay $246 million.

In a lawsuit filed in June against Los Angeles, inland officials accused the city and its airport authority of mismanaging the Ontario airport and of not doing enough to head off a 40 percent drop that brought passenger levels down from 7.2 million to 3.9 million since 2007.

The Inland Empire group's report blames Ontario airport's decline on an insufficient marketing campaign and an unfavorable fee structure for airlines.

Additional funds, the study states, ``will be needed to sharply reduce ONT charges (to airlines) and to provide aggressive marketing support.''

``Without such intervention, ONT is likely to continue to struggle just to maintain its current uncompetitive airport charge structure and minimal airport marketing program,'' according to the report.

The group rejected an invitation to restart negotiations by the previous Los Angeles mayor, Antonio Villaraigosa, who asked that the lawsuit be dropped.

Ontario councilman and Ontario airport authority president Alan D. Wapner said the study is a ``wake-up call'' to the new Los Angeles administration, led by Mayor Eric Garcetti.

``Time is running short to place the airport in the hands of the regional authority that has a vested interest in the airport making the greatest contribution to the region,'' Wapner said.

Ontario Mayor Pro Tem Jim Bowman said Los Angeles has a ``conflict of interest'' in running both the Ontario airport and LAX.

The existing ownership by LAWA, Bowman said, could result in ``dire consequences'' for the Inland Empire, he said.

``We hope to work with the new Los Angeles Mayor, Eric Garcetti, his Board of Airport Commissioners and a new LAWA administration to expedite the airport's transfer to the OIAA (Ontario International Airport Authority),'' he said.

Garcetti is in the midst of reviewing applications for board positions and department heads, including LAWA General Manager Gina Marie Lindsey.

Supporters of local control for Ontario say LAWA lowered the cost for airlines to fly into LAX while keeping the costs at Ontario high.

Lindsey has disputed the claim, saying in October that landing fees at Ontario are half what they are at LAX and terminal rental fees are necessarily high at Ontario in order to generate enough revenue to cover nearly $500 million in terminal and runway upgrades at the airport since the mid-1990s.

Lindsey said she supports selling Ontario airport ``if we can get to a reasonable price. We have always been open to discussing and negotiating a sales price. We have been opposed to giving a gift.''