"If you can take a commercial plane to get where you need to go at the time you need to be there, you should do it," she said in an e-mail. "If not, you have to look at alternatives such as trains, fuel-efficient vehicles, buses, and in some cases, private planes."
For that last option, Feinstein reimburses her husband, Richard Blum, for use of the jet, Gerber said. Blum bought the GIV for about $23 million in 1999. The reimbursements are based on a first-class commercial fare, with more than 90% of the money coming from Feinstein's personal funds and the rest from campaign coffers, the spokesman said. Last year, the reimbursements to Blum totaled about $73,000, he said.
But a GIV's operating expenses are much higher than a first-class booking. A round-trip Los Angeles-Washington flight on the Gulfstream burns about 4,500 to 5,000 gallons of fuel at a cost of roughly $20,000, depending on local pump prices, said Jeff Beck, a veteran corporate pilot. And that doesn't include pilot fees, maintenance and parking bills.
"It's the least environmental thing that politicians can do," Beck said. He said Gulfstreams devour so much fossil fuel per passenger that "it's like they're throwing dinosaur bones out of the tailpipe."
A coast-to-coast, first-class ticket on a major airline goes for about $1,200 to $2,500, round trip, according to a sampling of three airlines' prices Tuesday.
A Boeing 767-200 airliner burns about 1,550 gallons an hour -- three times as much as a GIV. But the larger plane typically can seat about 180 passengers, as opposed to a GIV's 12 to 14.
Eric Carlson, executive director of Carbonfund.org, a nonprofit that sells offsets, said it would charge $229 to cover the emissions from the GIV round trip.
Schwarzenegger flies a variety of leased jets, which cost his campaign $733,000 during the three months ending last September. Maile said the governor digs into his own pockets for some flights.
He also said Schwarzenegger has converted one of his Hummers to biodiesel fuel, and plans to install solar panels on his house. His other three Hummers remain gas hogs.
For her part, Feinstein drives a hybrid Lexus sport utility vehicle when she is home in San Francisco, Gerber said. But she drives a Lincoln Town Car in Washington.
Not that the eco-crowd is eager to criticize Feinstein and Schwarzenegger, who are generally viewed as key supporters of the growing movement to curb emissions.
Representatives of some environmental groups either would not comment on the two politicians' penchant for private jets, or suggested that allowances could be made in their circumstances.
"Given the exigencies of the campaign trail, if not the demands of governing of a large state, it may not be realistic to expect elective officials to fly commercial all the time," said Jon Coifman, spokesman for the Natural Resources Defense Council.
But O'Donnell, of Clean Air Watch, invoked a loftier ideal:
"It is fair to hope that our political leaders will lead by example."
Too expensive, some critics said. Too polluting, others said. Too much ado about nothing, the White House weighed in.
Aviation expert Mike Boyd said he thought high-profile announcements by airlines are akin to building a firebreak to show the industry is taking some action.
The new software will enhance aircraft safety, reduce fuel consumption, provide access to more airports and improve operational efficiency.
British Airways and Scandinavian Airlines System have established programs that give travelers the opportunity to pay carbon-offset fees to help fund clean technology projects.