Airlines and airports said they received no detailed warnings from the federal government that would have prepared them for the Sept. 11 attacks.

"No warnings indicated that a Sept. 11 scenario was credible or possible," United Airlines spokeswoman Chris Nardella told Foxnews.com.

"We’re not aware of any warnings or notifications of any specific threats," Delta spokeswoman Peggy Estes said from Atlanta.

"We were not notified by the federal government," echoed Barbara Platt, spokeswoman for Massachusetts Port Authority, which runs Boston’s Logan Airport, departure point for the two planes hijacked by alleged Al Qaeda terror network operatives and crashed into the World Trade Center. "We were not given specific notification."

None of the airline or airport spokespeople contacted would speculate on what they might have done differently had they received "specific" warnings. Until Feb. 19, the airline industry was responsible for airport security checkpoints.

And it's uncertain whether they could have prevented a Sept. 11 attack since neither the Federal Aviation Administration or the Federal Bureau of Investigation has ever distributed information on specific threats.

The FAA did issue general warnings to airlines and airports of possible hijacking scenarios, a government official, speaking on condition of anonymity, said Thursday. The written warning did not include any detailed information and was similar to several FAA notices earlier in the year, the official said.

National Security Adviser Condoleezza Rice said Thursday that airlines were specifically warned in August that terror groups were developing ways to carry out hijackings using "disguised weapons" such as key chains and cell phones.

But, she said, "I don't think that anybody could have predicted that these people would take an airplane and slam it into the World Trade Center, take another one and slam it into the Pentagon."

Rice said it would not have made sense to shut down the civil aviation system based on a non-specific analytic report on possible threats.

FAA Administrator Jane Garvey and other agency officials did not order any new security measures, in part because they have known for years of general threats made by Usama bin Laden, agency spokesman Scott Brenner said.

"This is a threat we've been watching intensely since 1998 when bin Laden made some very public statements," Brenner said. "While we were watching these groups, we never had a credible hijacking threat. It was never, 'This group was going to do a hijacking."'

Nardella said United, based in Elk Grove Cillage, Ill., has never gotten a specific alert, especially one that detailed a plane-as-missile scenario.

"Carriers receive security alerts and cautions from time to time in our daily interface from government agencies, but they’re typically general in nature," Nardella said.

Fox News' Michael Park and The Associated Press contributed to this report.