The crash of a UPS cargo plane in Birmingham, Ala., early Wednesday morning, which killed the two pilots, marked the second deadly plane crash for the Sandy Springs-based shipping giant in four years.

Investigators on the scene are expected to probe a number of possible causes, such as mechanical issues, pilot fatigue, or whether cargo may have contributed to the crash. The National Transportation Safety Board is sending a representative to UPS Airlines’ headquarters in Louisville, Ky., to examine training and maintenance records.

The Airbus A300-600F jet coming from Louisville crashed as it came in for a landing at Birmingham-Shuttlesworth International Airport at 5:11 a.m. CDT. There was no distress call from the pilots, according to the National Transportation Safety Board’s initial findings.

NTSB board member Robert Sumwalt said at a briefing late Wednesday afternoon that the tail section of the plane was still smoldering, preventing investigators from getting the “black boxes” — including the flight data recorder and cockpit recorder — that provide vital information on what transpired aboard the aircraft before the crash.

“We are optimistic we will be able to get there quickly and get those recorders,” Sumwalt said.

“Our goal is to find out not just what happened, but more importantly, why it happened so we can keep it from happening again,” he said.

Flight 1354 struck trees as it descended before crashing in an open area near the intersection of Treadwell and Tarrant Huffman roads near the Birmingham airport. It was about a half-mile north of Runway 18, according to Federal Aviation Administration spokeswoman Kathleen Bergen.

Birmingham Mayor William Bell said the plane went down in an area that once was a neighborhood but is now owned by the airport. Homes there were torn down years ago.

“Apparently the plane came in too low,” crashing into the side of a small hill, with the wing and tail catching fire on impact, Bell said.

The aircraft’s path from the initial ground impact to its final resting point was about 200 feet long, according to the NTSB, which encouraged local residents who had debris in their yard to contact them.

Pieces of the plane were strewn across the lawn of Barbara Benson, who lives close to the crash site. The plane also sheared off treetops next to her house.

“I woke up to a big ball of fire,” Benson said. “I thought it was Judgment Day.”

Sharon Wilson, who lives on Treadwell Road, was getting ready to go to the gym when she heard the plane come over the house.

“It terrified us,” Wilson said. “It was just a big boom” that shook the house.

Another nearby resident, Ryan Wimbleduff, said he saw fiery debris rolling down the hill, adding that his mother became hysterical.

And Lonnie Davis, who also lives nearby, said, “Only by the grace of God were all of us not blown away.”

The Birmingham crash comes after two other aircraft incidents in recent years at the shipping giant, including one in 2010 in Dubai in which a UPS Boeing 747 crashed on take-off, killing the two pilots. A United Arab Emirates government investigation implicated lithium ion batteries, which were being carried as cargo.

The report issued by the General Civil Aviation Authority of the UAE said a fire developed in cargo in pallets and “escalated rapidly into a catastrophic uncontained fire.”

When the report on the Dubai incident was issued last month, UPS said it ordered 1,821 fire-resistant shipping containers to be delivered starting in September.

In 2006, a UPS plane made an emergency landing in Philadelphia because of an on-board fire. The NTSB pointed to inadequacies in a variety of areas, including transport of lithium batteries on aircraft. No one was seriously injured in that incident.

It’s unclear whether lithium ion batteries were on the flight to Birmingham, or if fire-resistant containers were on the plane.

Former NTSB chairman Jim Hall said the Birmingham crash underscores the potential consequences when things go wrong on cargo flights.

“Even though there aren’t passengers on board, these can be devastating tragedies,” Hall said.

It’s too early to tell if pilot fatigue was a factor, but he said he thinks it will “highlight the concern many of us in the safety community have” about the exemption of cargo pilots from a rule aimed at combating pilot fatigue.

Pilot fatigue has been pointed to as a contributing factor in some crashes, and a new rule sets new limits on the amount of time passenger airline pilots can work. It will not not apply to cargo pilots.

Flight Safety Foundation president Kevin Hiatt said UPS and competitor FedEx have worked on fatigue counter-measures because of the heavy nighttime flying they do.

He said his organization is conducting a study to determine what contributed to this crash, as well as to the Asiana Airlines crash in San Francisco and the Southwest Airlines hard landing at New York’s LaGuardia Airport last month.

“We’ve gone for two years without a major incident in the United States, and we have seen three accidents in the last 30 days,” Hiatt said. “Have we become complacent, is there something with the technology of these airplanes, is there something with the training of the pilots?”

UPS is the second biggest company based in Georgia and the world’s largest package delivery company. The company has a fleet of more than 250 airplanes, including the Airbus A300.

The A300 that crashed was delivered new to UPS in 2003. The first Airbus A300-600F, a twin-engined wide-body cargo plane, entered service in 1994 and went out of production in 2007. About 104 of them are still in service, 53 belonging to UPS.

Airbus sent its own team of specialists to Alabama, saying it will provide technical assistance to the French BEA and authorities responsible for the accident investigation.

“This incident is very unfortunate, and our thoughts and prayers are with those involved,” said UPS Airlines President Mitch Nichols in a written statement Wednesday. UPS and Airbus expressed their sympathies for the victims and their families.

On ups.com, tracking numbers for impacted packages will show “Transportation Accident Occurred” as the exception code.