Reporter: Investigators got their first daylight look at the charred wreckage of the first deadly crash of a 777. Having gotten the voice record ers, the national transportation safety board is... See More
Reporter: Investigators got their first daylight look at the charred wreckage of the first deadly crash of a 777. Having gotten the voice record ers, the national transportation safety board is already gathering clues. A call to initiate a go-around occurred 1.5 seconds before impact. Reporter: The south korean airline, asiana, has a good safety record. Just as investigators were arriving on the scene, though, the airline ceo was already proclaiming the crash was not caused by a mechanical problem. "From what I know, the 777 aircraft and the engines did not have any problems," he said. And he defended the flight cruel as veterans. One with 9,000 flight hours, the other 3,000, the combined 10,000 hours. In reality, this crash could have been caused by many factors, machine and human. There are several systems to help pilots. One, an electronic system beams information to the plane, to tell the pilot if he's on the right landing path. In san francisco, that system has been shut off since june because of construction. An alternative? A series of lights along the runway. All white, the plane is too high. All red, too low. White and red means it's the right path. An airport official says he's not sure if those lights were on. And the 777 can set its own path, using gps, which is available at this airport. But even if none of those aides is turned on, there's the old fashioned way, in which the pilot sets the right decent, using knowledge and eyesight on a clear day. And perhaps they found themselves too low, too slow. As they came in over the water. Maybe there was some depth perception problems, they felt they were too high when actually they were where they needed to be. Reporter: This is only the second 777 crash in the jet's 18-year history. But the two crashes are eerily similar. Both came at landing. The key information from the ntsb and the black boxes today is that seven seconds before impact, the pilots called out for more power. And just a second and a half before the crash, there was a call to go around. But it was too late and the 777 hit the sea wall. David? That sea wall right here behind me. Abc's david kerley in washington for us tonight. I want to bring in john nance tonight. He's been with me since the story broke yesterday. I want to get to this image, showing the plane so low over the water as it was coming into the runway here. You know this airport well as a pilot yourself. The second image appearing to show the plane beginning to tumble right after that crash landing what do you see when you look at those new aim js out? The first image tells me he's not even low, maybe 300 feet below where a normal pilot would be on approach to san francisco's left runway, or any of those. It's a visual day. I don't have any understanding of why he would be so low and dragging that airplane in across the water. The second image is very fascinating and very -- well, put it this way. I'm very thankful this airplane was strong enough to hold up. It almost went over. If it had gone upside down, we would have had a totally different situation with rescuing those folks. It's a pain, if you wy to the strength of the wing that it didn't snap off. John, I wanted to get back to what david kerley just reported. From the cockpit, seven seconds before the impact, a call for more power. And then 1.5 seconds before the crash, the pilot asking for another go-around here at the air port. It's an indication, david, that he realized at the last second that they were not going to make it to the runway. But why did they not realize that ahead of time? Going to be one of the key questions here. Certainly was no mystery they were very low and why they waited this long is going to be one of the key elements of the investigation.
This transcript has been automatically generated and may not be 100% accurate.