WASHINGTON - (AP) - The FBI and Homeland Security have issued anationwide warning about al-Qaida threats to small airplanes, justdays before the anniversary of the 2001 terrorist attacks.

Authorities say there is no specific or credible terroristthreat for the 10-year anniversary of the attacks on the WorldTrade Center and Pentagon. But they have stepped up security acrossAmerica as a precaution.

According to a five-page law enforcement bulletin issued Friday,as recently as early this year, al-Qaida was considering ways toattack airplanes.

The alert, issued ahead of the summer's last busy travelweekend, said terrorists have considered renting private planes andloading them with explosives.

"Al-Qaida and its affiliates have maintained an interest inobtaining aviation training, particularly on small aircraft, and inrecruiting Western individuals for training in Europe or the UnitedStates, although we do not have current, credible information orintelligence of an imminent attack being planned," according tothe bulletin obtained by The Associated Press.

The bulletin also says al-Qaida would like to use sympatheticWesterners to get flight training, then get them to become flightinstructors.

Matthew Chandler, a spokesman for the Department of HomelandSecurity, described the bulletin as routine.

"We shared this information with our partners to highlight theneed for continued awareness and vigilance," he said.

Aviation security is much tighter than it was a decade ago, butal-Qaida remains keenly interested in launching attacks onairplanes, believing large attacks with high body counts are morelikely to grab headlines.

Threats to small airplanes are nothing new. After the 2001attacks, the government grounded thousands of crop dusters amidfears the planes could be used in an attack.

In 2002, U.S. officials said they uncovered an al-Qaida plot tofly a small plane into a U.S. warship in the Gulf. And in 2003,U.S. officials uncovered an al-Qaida plot to crash anexplosives-laden small aircraft into the American consulate inKarachi, Pakistan.