US investigators have found no evidence thus far pointing to terrorism in the disappearance of Malaysia Airlines Flight MH370 three weeks ago.
House Intelligence Committee Chairman Mike Rogers and Senate Intelligence Committee Chairman Dianne Feinstein, 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.
US officials close to the investigation 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 777 airliner on Sunday, days before the batteries in the locators attached to its black boxes are set to die.
The Malaysian government has said it believes the plane's course was altered as a deliberate act, but it remains unclear by whom, or whether the change was made in response to a technical fault.
Rogers said US 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 programme, 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 identified in the Indian Ocean than those made public, Feinstein said she had not and suspected intelligence officials did not have such images.
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 defence and that kind of thing," she said.