LOUISVILLE, KY. (WDRB) -- NTSB investigators looking into the fatal crash that killed two UPS pilots said the engine appeared to be working "normally" and that the flight controls were "consistent" with what is "expected."

During a news conference Saturday afternoon, NTSB board member Robert Sumwalt said investigators also want to take a closer look at surveillance video and want to know the mental and physical state of the pilots 72 hours before the crash.

Part of that examination will include interviewing UPS employees in Louisville to determine if the two pilots used the "sleep rooms" at UPS Worldport before departing for Birmingham, Alabama Wednesday morning.

The A-300 cargo jet crashed while attempting to land at Birmingham's airport. The pilots killed were: Captain Cerea Beal, Jr., of Matthews, North Carolina, and First Officer Shanda Fanning, of Lynchburg, Tennessee.

"We know they obtained keys to the sleep room in Louisville. UPS has sleep rooms available. We want to see if they actually used those rooms," Robert Sumwalt with the NTSB said Saturday.

This is the fourth day of the investigation into the deadly crash that killed two UPS pilots in Birmingham, Alabama.

While NTSB investigators said they have found no problems with the plane's controls, the two pilots did receive a "sink rate alert" meaning the plane was approaching the ground too quickly.

Investigators now want to study the pilot's sleep and work habits 72 hours before the crash.

An NTSB investigator said surveillance footage from the airport and Alabama National Guard base shows the plane on fire.