SAN FRANCISCO -- American Airlines grounded hundreds more flights Friday -- including over 20 at Bay Area airports -- as the inspection-related mess frustrated passengers and hurt an industry already bleeding cash thanks to high fuel costs.

Only two of six American Airlines flights originally scheduled at Oakland International Airport Friday will operate, spokeswoman Rosemary Barnes said. Two inbound and two outbound flights were canceled, she said.

There will be one American Airlines departure and one arrival Friday, and passengers are asked to check airline Web sites to confirm flight status before leaving for the airport, according to Barnes.

Eight inbound and five outbound flights have been canceled at San Francisco International Airport, airport duty manager Michael Brown said. Brown could not confirm how many American Airlines flights were originally scheduled to operate at SFO.

About 12 American Airlines flights will depart and 12 will arrive at Norman Y. Mineta San Jose International Airport as scheduled, according to airport spokesman David Vossbrink. Those flights are all scheduled to use an MD-80 aircraft, which Vossbrink said is a good sign that flights will continue to return to normal.

The airline is taking it day by day, Vossbrink said. "It looks like today is a lot better than yesterday."

American Airlines did however cancel four departures from San Jose Friday, three of which were scheduled to travel to Dallas and one that was scheduled to fly to Chicago, Vossbrink said.

Three flights scheduled to arrive at the airport Friday - two from Dallas and one from Chicago - also were canceled, according to Vossbrink.

In Washington, D.C., lawmakers were asking questions while fed-up air travelers around the country headed for trains. Others gave the airlines a pass, saying the companies were doing the best they could.

"If somebody's got a choice between being in a plane crash and being late, is there a choice?" Jane Bernard, a writer from New York who was delayed by at least three hours en route from LaGuardia Airport to Miami, said Thursday.

Mingo Valencia, a 60-year-old stuck at Hartsfield-Jackson Atlanta International Airport while heading home to Midland, Texas, wasn't so gracious.

"Poor management," he said bluntly.

Congress also weighed in Thursday. The Federal Aviation Administration official who ordered safety audits last month, Nicholas Sabatini, faced tough questions from a Senate subcommittee about the agency's lax oversight of airlines and his own accountability for recent breakdowns. The FAA noted that airlines had 18 months to check electrical wiring on MD-80 jets since an initial order was issued in September 2006.

American, a unit of Fort Worth, Texas-based AMR Corp., canceled another 595 flights Friday, bringing this week's total to nearly 3,100 due to safety inspections of its MD-80s. The carrier said disruptions will continue through Saturday as it works to comply with the federal safety order.

Alaska Airlines, Midwest Airlines and Atlanta-based Delta Air Lines Inc. joined the wave, each canceling a small number of flights on MD-80 aircraft Thursday.

At least 250,000 passengers have been affected by the American cancellations this week alone.

Other carriers like Continental Airlines Inc., JetBlue Airways Corp., AirTran Airways and Northwest Airlines Corp. said they passed the first round of FAA audits with a clean slate and did not expect extra maintenance work or flight delays. It was impossible to say whether that could change since the FAA is conducting another round of safety audits.

The cancellations come at a time of high fuel prices and mixed success among the major air carriers at getting domestic fare increases to stick. The fact that airplanes are flying very full is making it difficult for airlines that cancel flights to find empty seats on other carriers to rebook their passengers.

"This disruption is severe," said Webster O'Brien, an industry expert with aviation consulting firm Simat, Helliesen & Eichner. "People are going to be unhappy. There isn't going to be an easy way to walk everybody out of it."

American CEO Gerard Arpey said Thursday that the cancellations will cost the airline "in the tens of millions of dollars." Analysts say the toll could easily be that, and perhaps much more.

Besides lost revenue from the canceled flights, American also was giving $500 travel vouchers to an unspecified number of inconvenienced passengers and putting some travelers up in hotels. There also could be transportation costs to and from hotels, extra overtime for employees and the long-term costs of losing goodwill among customers.

American spokeswoman Andrea Huguely said the cost probably wouldn't be known until Saturday night, when the carrier expects to have all its MD-80s back in service.

The cost to other airlines also was unclear, and the pain could continue, analysts said.

"Just given the level of scrutiny, it wouldn't surprise me if there were more cancellations and groundings at other airlines," said Standard & Poor's analyst Philip Baggaley.

He said the disruption was worse than some major storms that have affected large airline hubs.

"The costs are fairly substantial," Baggaley said. "Given that the cancellations have been spread among a number of carriers, this will make it harder for airlines to turn around and try to raise fares, particularly in the weakening economy. It does indeed come at a bad time."

Some travelers looked for other modes of transportation.

Amtrak has seen a spike in passengers since the flight cancellations began earlier in the week, especially in the Northeast, spokesman Cliff Cole said.

"Our ridership was heavy yesterday, is heavy today and is likely to be heavy tomorrow, based on our reservations," Cole said Thursday.

Greyhound Lines Inc. spokesman Eric Wesley said he was unsure whether demand had increased because many bus customers buy tickets at the last minute.