Electronic landing system was off at San Francisco airport during crash

Investigators have a lot of evidence to weed through 4:25

A navigational technology that steers commercial pilots to safe landings was not operational at San Francisco's airport Saturday when a South Korean airliner came in at an awkward angle and crashed on the runway, officials said.

San Francisco International Airport spokesman Doug Yakel said that a key component of the facility's instrument landing system that tracks and guides an arriving airplane's course was turned off.

The airport has turned off the system for nearly the entire summer on the runway where the Asiana flight crashed, according to a notice from the airport on the Federal Aviation Administration's Web site, Reuters reported. It showed the system out of service June 1-August 22 on runway 28 Left.

The so-called Glide Path technology, which calculates an airplane's path of descent and transmits the data to pilots in real time, is a commonly used but by no means essential tool, said Barry Schiff, a pilot and author who has written extensively about aviation safety.

"The system was designed to be used at nights or during inclement weather events, like fog," Schiff told NBC News on Sunday. "But it's not anything that's required on a clear, beautiful day like yesterday."

Asiana Flight 214 slammed on the runway in relatively favorable weather conditions — sunny skies, patches of clouds, and light wind.

Kevin Hiatt, chief executive of the Flight Safety Foundation and a former Delta Airlines pilot, said airports frequently take ground-based instrument landing systems offline for maintenance on clear days.

Schiff said pilots can use several other technological tools and visual cues to make descents on a clear, crisp day. And yet, according to Schiff, the unidentified pilot of the Boeing 777 somehow could not manage to make a stable, steady landing Saturday.

"He showed a lack of skill, a lack of recognition that he was coming in too low and too slow," Schiff opined. "He should have recognized that before he got to the seawall. If he had, everything would have turned out fine."

"That's the big mystery," Schiff added. "Why didn't he recognize that?"

Federal investigations announced Saturday that it was too premature to determine a cause of the horrific crash, which killed at least two people and injured more than 100 others. A team from the National Transportation Safety Board assumed control of the probe late Saturday and was sifting through various evidence on Sunday — and it could be months or even years before the exact reason for the crash is known.

Schiff said he thinks many commercial pilots rely far too heavily on technologies like Glide Path and not enough on human intuition and skills -- a sentiment that has been voiced by Mary Schiavo, the former Inspector General of the U.S. Department of Transportation, according to Reuters.

"Pilots are becoming more and more dependent on automization and computerization," Schiff said. "And when they're called upon to revert to old-fashioned abilities," they can make mistakes.

The Federal Aviation Administration has advocated for flight training that includes instruction in "manual" forms of flying and traditional practices, Schiff said.

Reuters and Julie Yoon, F. Brinley Bruton and Matthew DeLuca of NBC News contributed to this report.

National Transportation Safety Board Chairman Deborah A.P. Hersman and Investigator-in-Charge Bill English look at interior damage to Asiana Flight 214 during their first site assessment in San Francisco, California. Ho / AFP - Getty Images