A confidential government report issued last month, which states that the nation's aviation system remains vulnerable to terrorist attacks, reveals nothing new, a Department of Homeland Security official told FOX News on Monday.

The report, compiled by the Department of Homeland Security and the FBI, does gather all available intelligence on civilian aviation vulnerability security into one single package, officials said, making it a useful guide to improving security.

Despite billions of dollars worth of security investments, commercial airlines remain a target for terrorists, the report says. It adds that Al Qaeda appears determined to study and test new American security measures to "uncover weaknesses."

The report, released to law enforcement officials on Feb. 25, was first disclosed to the general public Sunday evening by the Web site of The New York Times.

It suggests that terrorists may try to rent or steal civilian or business aircraft housed at small "general-aviation" airports, which have little or no security.

"Even though our airliners are a lot better protected than they were before Sept. 11, if you look at general aviation, the smaller carriers and other ways you can get aircraft in this country and try to pull off some kind of similar attack — I think it could still be done," Sen. Jon Kyl (search), R-Ariz., chairman of the Senate Judiciary Subcommittee on Terrorism, Technology and Homeland Security, told FOX News on Monday.

A counterterrorism official said intelligence that surfaced last August singled out helicopters as potential targets. That intelligence led DHS to raise the terror alert level in Washington, New York and northern New Jersey to protect financial institutions.

The report concludes with what officials have long said — that terrorists looking for weaknesses in the security system will look for the path of least resistance.

Federal officials said they were continuing to improve airline security, as well as safeguard private planes and helicopters.

A Department of Homeland Security (search) spokesman told FOX News that the assessment is "an example of sharing comprehensive information about potential aviation security threats to state, local, and private sector security officials, who are our partners in helping secure the U.S. aviation system."

One lawmaker said security was much better than it was before the Sept. 11, 2001, terror attacks, but no one should be "surprised that there are still challenges, imperfections."

"You're seeking perfection, and there is no such thing," Sen. Trent Lott (search), R-Miss., told FOX News. "You've got to do a better job in protecting commercial aviation.

"We're still threatened. We still have to be vigilant ... we have to do it for months and years to come," Lott added, suggesting that port and train security should also get more attention. "This is like Swiss cheese. It's very hard to fill every hole."

So far, more than $12 billion has been spent on explosive detectors, armored cockpit doors, screeners, air marshals and other aviation security systems since the Sept. 11 attacks.

President Bush has proposed giving the Transportation Security Administration (search) $5.6 billion in 2006 — $2 billion of which would go to airline passenger screening, and $1.45 billion for airline baggage screening.

But a report by congressional investigators in December found that TSA "has primarily focused on strengthening the security of commercial aviation."

The agency had not thoroughly assessed the risks posed by small private planes, failed to issue meaningful threat information to general-aviation airports and hadn't made sure charter airlines and flight schools complied with security regulations, the congressional report stated.

The report's leak to the press came on the heels of news that Abu Musab al-Zarqawi (search), the top Al Qaeda terrorist in Iraq, was planning an attack on U.S. soil.

Time magazine reported this week that a restricted bulletin recently issued to U.S. security agencies indicated that Zarqawi was planning to attack "soft targets" such as schools, restaurants and movie theaters.

Kyl said the risk of attack was one Americans were forced to take as part of the price of living in a free society.

"We've always known that soft targets in the United States can not be protected," he said. "We're a huge open country. And if you stop and think for a moment, anyone who wanted to set off a car bomb, for example, anywhere in this country, would be able to do it."

The latest intelligence indicates that Zarqawi thinks terrorists can get into the United States through Mexico.

A captured Zarqawi lieutenant told U.S. intelligence officials that Zarqawi thinks that "if an individual has enough money, he can bribe his way into the U.S."

Kyl questioned the credibility of the statements.

FOX News' Kelly Wright and The Associated Press contributed to this report.