GEORGETOWN, Guyana - The airport where a Caribbean Airlines jet skidded off a rain-slicked runway and broke apart is upgrading systems that help pilots to land, but all the new systems weren't yet operating at the time of the crash, Guyana's top aviation official said Sunday.

Officials and aviation experts cautioned it was far too early to say if the lack of the systems was a factor in the crash that injured about 30 people but miraculously caused no deaths. The Boeing 737-800, with 162 people on board, slid off the end of the runway and stopped just short of a deep ravine near the South American country's capital.

Canadian company Intelcan is installing an instrument landing system at Cheddi Jagan International Airport as part of a $3.5 million upgrade in pilot aids. Civil Aviation Director Zulfikar Mohamed said the changes should be operational soon.

"Things will be better with a new ILS system that we are testing," Mohamed told The Associated Press.

An ILS helps pilots land by giving them a more precise reading of their angle of descent and the position of the aircraft down to 200 feet. It is especially helpful at night and when there is low visibility, although officials said Sunday that visibility apparently was not a factor in the accident.

Mohamed said there was light rain but visibility was 8 kilometres at the time the plane landed early Saturday. Paula McAdam, deputy director of the Civil Aviation Authority, said that "visibility was excellent for flying" at time of crash.

The U.S. National Transportation Safety Board announced it had dispatched a team to Guyana to assist with the investigation. It includes experts in operations, meteorology, airworthiness, survival factors and aircraft performance.

The NTSB also lowered the number of people on board the plane by one, to 156 passengers and six crew members. The airline had said Saturday that there were 157 passengers and six crew.

Aviation experts say mishaps such as these are typically a result of a combination of factors and conditions. Possibilities during Saturday's rainy pre-dawn darkness include a sudden microburst, a malfunction or a misjudgment of the approach and landing by the pilots.

Patrick Smith, a commercial pilot who has flown into Guyana, said that in addition to the lack of the ILS, which is in place at most large and busy airports, the runway can be challenging because it is relatively short. But he said the runway is in good shape, the air traffic controllers are experienced and it's not an unsafe place to fly.

"Importantly, all these things together do not make the airport unsafe by any stretch," said Smith, who runs a website on aviation at www.askthepilot.com, in a phone interview from Boston, Massachusetts. "They do make it more challenging, less forgiving."

Mohamed said he would like to see the runway lengthened by about 2,500 feet, though the country does not have the money for the extension.

Scott Johns, a Denver-based former Air Force pilot and accident safety investigator who reviewed photos and other information about the incident, said it appeared the crew might have been in a less-than-optimal position on approach.

"It seemed like the crew perhaps made a decision to continue with a landing after an approach that was either fast or high or both," he said in an email.

The airport's relatively basic conditions were also evident in the response to the crash.

For more than an hour after the aircraft ran off the runway, rescue teams were groping in darkness, using flashlights and beams from fire engines and other vehicles to illuminate the area where the aircraft came to rest after splitting in two.

Transport Minister Robeson Benn said the government is "looking at all those issues like lighting and other stuff, but it is not completed as yet."

Bill Voss, president of the U.S.-based Flight Safety Foundation, noted that despite the dramatic crack in the jet after the crash, the incident follows in the path of similar recent overshoots and crashes with no or few fatalities, evidence of design improvements throughout the aircraft.

"It is really impressive. The engineers have gotten some things right," said Voss, whose industry-supported group promotes aviation safety worldwide, speaking from Alexandria, Virginia.