Fifth District Supervisor Josie Gonzales is leading the charge to ensure that tens of thousands of residents aren''t overwhelmed by noise from low-flying aircraft.

The March Joint Powers Authority, the public entity created to address the reuse of March Air Reserve Base, is looking at ways to relieve noise from cargo planes now flying over Riverside County.

Officials are considering testing new flight paths for DHL planes leaving the base.

The preferred alternate route would take planes over the southern parts of Colton, Rialto and Bloomington toward Pomona.

About 75,000 people under the proposed flight path would be exposed to noise of 75 decibels from each airplane, according to a consulting firm hired by March JPA.

"If this is ever approved, it will be a great disservice to the residents of San Bernardino County because they will get all the noise and pollution," said Catherine Barrett-Fischer, executive committee chairwoman of the Community Alliance for Riverside''s Economy and Environment, a grass-roots group concerned about the development of surplus land at the March base.

In addition to the potential early morning noise impacts, Gonzales is concerned that DHL planes would jam already crowded airspace used by L.A./Ontario International Airport and San Bernardino International Airport.

Gonzales has asked San Bernardino County officials to investigate the possible shift in cargo flights.

"If staff determines the DHL proposal would harm our residents or air traffic, I will call a meeting so we can discuss a strategy for defeating it," Gonzales wrote in a June 7 letter to Colton, Rialto and San Bernardino city officials.

Gonzales also has asked March JPA staff members to consider other noise-control measures besides shifting flight routes.

Rep. Joe Baca, D-Rialto, said he is "vehemently opposed" to any plan that would direct cargo planes over heavily populated areas in San Bernardino County.

Baca said Riverside County officials and the Federal Aviation Administration must explore adjusting flight schedules and upgrading DHL aircraft technology before resorting to a change in flight patterns.

"Failure to act will only continue to put the health and safety of residents in two counties, both on the ground and in the air, at risk," Baca wrote in a letter to Riverside County Supervisor Marion Ashley on Thursday.

FAA spokesman Ian Gregor said the agency is studying March JPA''s request to test new flight patterns. The evaluation could take weeks or months, he said.

"Generally speaking, any proposal to shift noise from one area to a lower-income area would encounter some serious environmental justice issues," Gregor said. "We don''t shift noise from (one) area to another for the sake of shifting noise. It''s sometimes done for safety and efficiency reasons."

Residents under the existing flight path complain that the noise from DHL planes is unbearable.

Up to eight older-model DC-9 cargo jets fly as low as 1,000 feet above homes between 2:30 a.m. and 4 a.m. several nights a week.

"It sounds like there''s a plane right on top of your house," said Frank Yorio, a 58-year-old Riverside resident who lives two miles from the March base under the flight path. "Sleeping through it is next to impossible for my wife and I."

DHL Americas spokesman Jonathan Baker would not say if his company would be willing to consider changing its hours of operation or improving its fleet with cleaner, quieter planes.

"We have been working with March JPA to address the community concerns and wish to be a good corporate citizen," said Baker, based in Plantation, Fla. "That''s all I can say at this point."

Riverside County Supervisor Bob Buster, a member of the March Joint Powers Commission, said the night flights must stop until the alternate routes are thoroughly studied.

Buster, the only member of the commission to vote against the environmental document in 2004 that allowed DHL to come to March, said he would work with Gonzales to ensure the problem isn''t unloaded on San Bernardino County residents.

"I don''t think it''s fair to move the noise and affect people elsewhere," Buster said.