California’s high-speed trains — armed with the potential for cheaper fares and peaceful trips — could steal about 6 million passengers each year from the three Bay Area international airports combined, estimates show.

The $42.6 billion San Francisco-to-Los Angeles bullet train expected to begin operation in 2020 could directly cause San Francisco International, Norman Mineta San Jose International and Oakland International airports’ operations to drop 6.1 percent, an independent report released this week says.

San Jose would be hit hardest, according to consultants at SH&E, a Virginia-based aviation firm the Metropolitan Transportation Commission contracted to study the bullet train’s impact on Bay Area airports. Airport executives, Bay Area officials and transportation experts will review the report through an MTC panel Friday.

SH&E forecasts that by 2035 the San Jose airport would lose 12 percent of its projected passengers because of high-speed rail, followed by a 9 percent diversion at Oakland International and a 4 percent loss at SFO. They figure the airports would carry slightly more than 100 million total passengers without the bullet train but that each would carry about 2 million fewer if high-speed rail is built as planned.

Translated to total airport activity, the train project is estimated to reduce overall operations at the San Jose airport by 9.2 percent, at SFO by 5.3 percent and at Oakland International by 5.2 percent.

“There will be a giant sucking sound as you hear, especially business travelers, vacate airplanes in favor of high-speed rail,” said Henry Harteveldt, a travel industry analyst with Forrester Research in San Francisco, who was not involved in the study. “It will be less susceptible to delays, more efficient, (will go) city center to city center, and there are just some additional pleasantries.”

California airports have long been supportive of the rail project. There are stations planned at a BART stop from SFO in Millbrae, in San Jose and near Southern California airports.

“Our initial forecasts indicate that any losses in short-haul passenger traffic would be offset by increases in passengers using high-speed rail to connect to SFO to fly long-haul and international flights,” said SFO spokesman Mike McCarron.

The study indicated the diversion estimates represented “total aircraft activity.”

“I don’t see someone taking high-speed rail so much going to SFO and LAX and using that to go international,” said MTC Planning Director Doug Kimsey. “There may be some, but that’s not their primary market by any stretch.”

Nearly all the fliers lost would be Bay Area travelers headed to the region from Los Angeles to San Diego, the consultants said.

High-speed rail planners estimate a ride from the Bay Area to Southern California would cost about $105, or 83 percent of the average comparable airfare, estimated to be $125. A trip from San Francisco to Los Angeles would take about 2½ hours.

The consultants figured two-thirds of SFO and San Jose airport travelers headed to the Los Angeles and Burbank areas would switch to high-speed rail, and about half the Oakland passengers would do the same.

The next most popular destination markets prime for Bay Area fliers to convert to high-speed rail were Long Beach and Orange County (about half of SFO and San Jose airport travelers would switch) followed by Ontario, Palm Springs and San Diego (about 20 percent diversion estimated at SFO and the San Jose airport). There would also be some passengers headed to the Central Valley who would switch.

The consultants noted a few factors could change their estimates, namely the final high-speed rail fare and trip time, security screenings for bullet train passengers and how airlines react.

Quick Acela Express trains have captured 62 percent of travelers between Washington, D.C., and New York and half the market from New York to Boston, Harteveldt said.

He predicted the airlines that fly from the Bay Area to Southern California, such as Southwest and United, would “not give up without a fight” but may use smaller aircraft — as they did in the Northeast — or move their planes to more profitable routes.

Overseas, airlines recently slashed prices in China to compete with new bullet train routes while European air carriers have largely ceded the battle with their high-speed rail competition, according to a China Daily report this month.

Mike Rosenberg covers transportation. Contact him at 650-348-4324.