BIRMINGHAM, Alabama (Reuters) - The UPS cargo jet that crashed in Alabama this week, killing its two crew members, was flying on autopilot until seconds before impact, even after an alert that it was descending too quickly, authorities said on Saturday.

"The autopilot was engaged until the last second of recorded data," said Robert Sumwalt, a senior official with the National Transportation Safety Board.

He said information retrieved by investigators from the flight data recorder aboard the United Parcel Service jet showed that its auto throttle also was engaged until moments before the fiery crash.

The Airbus A300 jet was approaching the runway at Birmingham-Shuttlesworth airport before dawn on Wednesday when it clipped the trees in an adjacent residential area and crashed into a steep embankment well short of the runway.

Sumwalt, who spoke at a media briefing near the crash site, had said on Friday that the pilots received a low altitude warning barely seven seconds before the sound of impact. He repeated that in his remarks on Saturday but did not say whether the alert had triggered any attempt by the crew members to disengage the autopilot as part of a last-ditch attempt to abort landing and re-gain altitude.

The pilots did not issue a distress call.

Sumwalt stopped short of saying there was anything unusual about a so-called "instrument approach" to the airport using autopilot.

But he said the NTSB would be looking closely into "UPS's instrument approach procedures" and how it typically went about guiding a large cargo hauler to touchdown on Birmingham-Shuttleworth's Runway 18.

That's the runway the UPS jet was approaching when it crashed and Sumwalt said the investigation would include a flight test at the airport in a UPS A300.

Kevin Hiatt, president and chief executive officer of the Flight Safety Foundation, anAlexandria, Virginia-based international watchdog group, told Reuters in an interview on Thursday that a "full instrument" landing was not highly advisable atBirmingham-Shuttlesworth.

The airport can be tricky to land at because it is nestled among hills that is especially true of Runway 18, said Hiatt.

Hiatt, a former Delta Airlines pilot, said he had touched down on the runway many times himself.

"It is not a full instrument landing. You have to visually fly into that runway," he said. "Sometimes it takes nuance to land there. You have to realize that hill is there or you could come in too low."

The crash occurred shortly before dawn in rainy conditions as low-lying clouds hung over Birmingham.

So far, Sumwalt said there was nothing to indicate the crash was caused by engine failure or any mechanical issues.

He also said the runway lights were examined and found to have been "within one one-100th of a degree of being properly aligned" at the time of the crash.

UPS has identified the dead crew members Cerea Beal Jr., 58, of Matthews, North Carolina, and Shanda Fanning, 37, of Lynchburg, Tennessee.

As a standard part of any accident investigation, Sumwalt said the NTSB was looking into the physical and mental well being of Beal and Fanning in the 72 hours before the accident.

Beal, the captain of the downed aircraft, had about 8,600 hours total flying experience, including more than 3,200 hours in the Airbus A300, according to the NTSB.

(Additional reporting and writing by Tom Brown; Editing by Bill Trott)