Moffett Field, Calif. ? An unprecedented national survey of pilots by the U.S. government has found that safety problems like near-collisions and runway interference occur far more frequently than previously recognized. But the government is withholding the information, fearful it would upset air travelers and hurt airline profits.

NASA gathered the information under an $8.5 million federal safety project, through telephone interviews with roughly 24,000 commercial and general aviation pilots over nearly four years. Since shutting down the project more than one year ago, the space agency has refused to divulge its survey data publicly.

After The Associated Press disclosed details Monday about the survey and efforts to keep its results secret, NASA’s chief said he will reconsider how much of the survey findings can be made public.

“NASA should focus on how we can provide information to the public, not on how we can withhold it,” NASA Administrator Michael Griffin said in a statement. He said the agency’s research and data “should be widely available and subject to review and scrutiny.”

Last week, NASA ordered the contractor that conducted the survey to purge all related data from its computers. Congress on Monday announced a formal investigation of the pilot survey and instructed NASA to halt any destruction of records. Griffin said he already was ordering that all survey data be preserved.

The AP learned about the NASA results from one person familiar with the survey who spoke on condition of anonymity because this person was not authorized to discuss them.

A senior NASA official, associate administrator Thomas S. Luedtke, said earlier that revealing the findings could damage the public’s confidence in airlines and affect airline profits. Luedtke acknowledged that the survey results “present a comprehensive picture of certain aspects of the U.S. commercial aviation industry.”

The AP sought to obtain the survey data over 14 months under the U.S. Freedom of Information Act.

“Release of the requested data, which are sensitive and safety-related, could materially affect the public confidence in, and the commercial welfare of, the air carriers and general aviation companies whose pilots participated in the survey,” Luedtke wrote in a final denial letter to the AP. NASA also cited pilot confidentiality as a reason, although no airlines were identified in the survey, nor were the identities of pilots, all of whom were promised anonymity.

Griffin said NASA will reconsider its denial for the data to the AP.

Among other results, the pilots reported at least twice as many bird strikes, near mid-air collisions and runway incursions as other government monitoring systems show, according to a person familiar with the results who was not authorized to discuss them publicly.