(Adds aviation expert, additional Feinstein comment)
WASHINGTON, March 30 (Reuters) - Senior U.S. lawmakers on Sunday said investigators had found no evidence thus far pointing to terrorism in the disappearance of Malaysia Airlines Flight MH370 three weeks ago, and that it was critical to find the plane to understand what happened on board.
House Intelligence Committee Chairman Mike Rogers and Senate Intelligence Committee Chairman Dianne Feinstein, speaking on Sunday talk shows, said they had seen no evidence of foul play.
"I have seen nothing yet that comes out of the investigation that would lead me to conclude that (this was) ... anything other than a normal flight that something happened and something went wrong," Rogers told "Fox News Sunday."
U.S. officials close to the investigation last week said the FBI examined data it received from a home-made flight simulator and other computer equipment used by MH370's pilots, but found nothing illuminating.
More than two dozen countries and 60 aircraft and ships continued to search for the missing Boeing Co 777 airliner on Sunday, days before the batteries in the locators attached to its black boxes are set to die.
Alan Diehl, who has 40 years experience investigating accidents for the U.S. government and military, urged President Barack Obama to offer Malaysia the use of larger numbers of U.S. P-3 Orions, Air Force MC-130 special forces transports, and U.S. submarines to hunt for the wreckage before the pingers die.
He told Reuters such efforts would be costly, but were needed for the victims' families, to deal with possible safety issues with the 1,100 777s now flying, and to avert a negative impact on future sales of Boeing's newest 777 model, the 777X.
"If in the next few years we are still wondering about the 'Malaysian Mystery', (airlines) may be reluctant to purchase aircraft suspected of having a flaw," Diehl said. "This could cost the company billions and America thousands of jobs."
Feinstein told CNN the Malaysian government was in charge of the search effort, and it would have to ask for additional search or intelligence resources from the U.S. government.
"You can offer but you cannot demand," Feinstein told CNN. "And so the Malaysians would have to ask.
The Malaysian government has said it believes the plane's course was deliberately altered, but it remains unclear by whom, or whether the change was made in response to a technical fault.
The Boeing 777 has one of the best safety records of any commercial aircraft in service. The only fatal crash came last July when Asiana Airlines Flight 214 struck a seawall on landing in San Francisco, killing three of the 307 people aboard.
Rogers said U.S. investigators would conduct a detailed forensic analysis of the computer equipment, even as they continue to investigate the crew and passengers of the plane, but he warned it would take "a tremendous amount of time."
"We're just going to have to be patient ... as this thing unfolds and the only way to really find out what happened is to try to find the airframe itself or as much of it is intact so they can do the forensic investigation on that," Rogers said.
Feinstein echoed those remarks on CNN's "State of the Union" program, saying she had not seen any evidence indicating a terrorist act brought the airplane down.
Asked if she had seen higher resolution satellite images of the possible debris spotted in the Indian Ocean than those made public, Feinstein said she had not, and suspected intelligence officials did not have additional data to offer the Malaysians.
She said the lack of sharpness in the images made public could be linked to the sophistication of the satellite that gathered the imagery, but declined to provide further details.
"You have to understand that American intelligence doesn't gear itself to be ready for plane crashes. That is not its job. Our job is terrorism and missile defense and that kind of thing," she said. (Reporting by Andrea Shalal; Editing by Jim Loney, Meredith Mazzilli and Bernard Orr)