The Federal Aviation Administration is finally collecting a trove of confidential safety data from commercial airline operators, but the agency is still “years away” from analyzing the information to predict problems and doesn’t even allow its own inspectors to look at the data, according to an internal auditor’s report.

As a result, most inspectors and analysts don’t use the Aviation Safety Information Analysis and Sharing system, the FAA’s inspector general concluded in one of three reports last week looking at safety, air traffic controller training and flight delays.

FAA officials keep delaying their target for being able to use the analysis system to predict and correct safety problems. The latest self-imposed deadline is five years away.

“Field-level inspectors may be missing important safety information applicable to their assigned air carrier,” the investigators wrote in their report about the safety analysis system, on which the government has spent tens of millions of dollars and for which it is requesting $15 million in 2014.

In terms of flights, the inspector general found that the number of delays and cancellations has dropped dramatically since 2000, thanks to airlines scheduling fewer flights, airports improving their own infrastructure and, perhaps most surprising, better all-around weather.

Although scientists warn that climate change could cause traumatic weather patterns, the government audit found improving skies for airlines in the past decade or so, leading to a drop in the number of weather-related flight delays.

Severe weather accounted for 30 percent of all flight delays in 2004, but that dipped to 24 percent in 2008 and 2009 and fell to 16 percent in 2012.

“Relatively favorable weather conditions over the last few years have contributed to the reduced number of delays across most of the country,” the audit said.

On the negative side of the ledger, airlines continue to overbook peak times at the most popular airports, despite the FAA’s effort to control the problem, and the government doesn’t have a good grasp on other structural reasons for delays, the inspector general said, pointing to more data that should be collected.

“Addressing these data problems would go far in giving key aviation stakeholders and the flying public a fuller understanding of air carrier flight delays and their causes,” the investigators said.

Still, delays have fallen by 33 percent since 2000, when the inspector general issued its first report on delays. The number of cancellations is down 56 percent at major airports.

The best improvement was in “extreme taxi times,” when a plane sits on the runway for at least three hours.

After the Transportation Department started imposing penalties in 2010, the number of extreme delays dropped from 1,630 in 2000 to 30 in 2012 — a 98 percent decrease.

Other major changes include airlines simply adding more time to the projects duration of each flight, which builds in extra room to accommodate problems.

The FAA, in its official response, said it also has improved air traffic control procedures and most other efficiency problems possible for now, and that a major upgrade of the system underway likely will take years.

“Improved causality data and ongoing schedule monitoring are useful for identifying systemic delays, but there will likely be diminishing opportunities for further reducing chronic delays until significant NextGen capacity enhancements begin to come online,” said Brodi Fontenot, assistant secretary for administration at the FAA.

As for the safety system, the FAA acknowledged that its hands are tied to some extent by the confidentiality agreements, but H. Clayton Foushee, director of the FAA’s office of audit and evaluation, said the secrecy is needed in order to get airlines to turn over information.

Even with those limitations, the system has helped officials adopt 16 major safety initiatives, Mr. Foushee wrote. He said officials are taking steps to try to get more data out the door.

“Over the next two years, the FAA will implement new initiatives to improve the communication of ASIAS identified risk factors with the inspector workforce. These new initiatives will provide actionable information that will enable FAA inspectors to focus their surveillance activities on higher priority risk areas,” Mr. Foushee wrote.