Flight recorders retrieved from UPS cargo jet in Alabama BIRMINGHAM, Alabama (Reuters) - An initial investigation into the wreckage of the UPS cargo jet that crashed on approach to Birmingham, Alabama's airport has found no evidence of pre-impact fire or engine failure, the National Transportation Safety Board said on Thursday. The downed plane's cockpit voice and flight data recorders were also retrieved. The so-called black boxes will be sent to the NTSB headquarters in Washington for evaluation of possible clues about the cause of the fiery crash of the United Parcel Service Inc aircraft in which two pilots were killed, Robert Sumwalt, a senior NTSB official, told a press conference in Birmingham. Sumwalt said the flight data and cockpit voice recorders were covered in debris and plastic that melted in the fire and then hardened onto them. It took three hours to dig them out. Investigators hoped to get them opened later Thursday and should know by Friday whether the data is still good. They weren't made to be opened. They'll have to saw into them," Sumwalt said. We are optimistic we will be able to obtain good data from those recorders. He said there was debris in the engine that was apparently sucked in when the plane clipped the trees. It was "indicative of an engine coming through trees and striking dirt," Sumwalt said. Sumwalt said they also would be looking at lighting and navigational issues that might be involved with the runway. The cargo plane, an Airbus A300, clipped trees and nearly hit a house before plowing across about 200 yards of empty field well short of the Birmingham-Shuttlesworth International Airport, the NTSB has said. The pilots of UPS flight 1354 issued no emergency or distress calls before the plane crashed and burst into flames. UPS identified the two crew members as 58-year-old Carea Beal Jr., a resident of Matthews, North Carolina, and Shanda Fanning, 37, of Lynchburg, Tennessee. Kevin Hiatt, president and chief executive officer of the Flight Safety Foundation, an Alexandria, Virginia-based international watchdog group, said Birmingham-Shuttlesworth can be tricky to land at because it is nestled into surrounding hills. That is especially true of Runway 18, which the UPS jet was approaching when it crashed into a tall hill at the north end of the airport, said Hiatt. A veteran former Delta Airlines pilot, Hiatt 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. Sometimes it takes nuance to land there. You have to realize that hill is there or you could come in too low," Hiatt told Reuters. The crash occurred shortly before dawn in rainy conditions as low-lying clouds hung over Birmingham. "They were slanted south, coming in at a straight approach," Hiatt said of the ill-fated UPS pilots. "Since there was no distress call, everything seemed to be progressing normally," he said. They must have gotten blindsided by something that happened, perhaps with the engines. Writing by Tom Brown; Editing by Lisa Von Ahn, Phil Berlowitz and Andre Grenon