Another site detailed special gatherings at Minot Air Force Base in North Dakota, while yet another accepted orders for maps of military installations.
No longer.
Concerned they could be aiding terrorists, some government and private Web sites have decided to stop sharing quite so much potentially sensitive data.
Such self-censorship wouldn't prevent terrorists from turning to libraries or even other Web sites for information that could be useful in attacks.
``But that is not a justification for publishing it in easily accessible ways. Let them work for it,'' said Steven Aftergood, senior research analyst at the scientists' group.
The private organization removed from the Web its research containing locations, building layouts and aerial images of intelligence offices, some unacknowledged by the U.S. government. Also removed were details on nuclear sites abroad.
Minot removed clues about where personnel may be gathering, including schedules of activities and locations of military housing units.
The National Imagery and Mapping Agency suspended online and offline sales of maps of military installations as well as its highest-resolution maps of other U.S. locations.
The U.S. Office of Pipeline Safety now restricts its mapping software and pipeline data to industry and government officials, while the Environmental Protection Agency removed information on chemical plants and their emergency response plans.
``People have a right to know what kinds of risks there are, but unfortunately terrorists are people, too,'' said Jim Makris, the EPA's emergency coordinator.
The reports are still available in EPA reading rooms, but Makris said identification is required.
Jeremiah Baumann of the U.S. Public Interest Research Group, a private watchdog organization, criticized the EPA's decision and said the data ``would not be very useful to terrorists.''
Still, Baumann's group took down a 1999 report based on the EPA data to avoid provoking a debate on public disclosure at this time.
Censorship is also occurring for non-security reasons.
Some online forums have deleted hate messages attacking Muslims. A news site, Irish Republican Activist Radio, suspended operations out of fear it may be accused of supporting terrorism and have assets seized.
The removed or restricted materials represent only a tiny chunk of what's available on the Internet, but First Amendment advocates worry that this is only the beginning.
``It's a fine balance that must be struck here, but in wartime, the temptation is always to greater censorship rather than less,'' said Adam Powell, vice president for technology and programs at The Freedom Forum.
In the meantime, the Internet still has plenty of information that could potentially aid terrorists.
Airports publish terminal maps, while amateur astronomers post fly-by schedules of satellites, letting terrorists know when to duck. Boeing Co. and other sites disclose fuel capacity of aircraft.
One site sells videotapes of the cockpit where ``the Captain explains every major instrument and avionics system.''
It's unclear the extent to which terrorists used the Net to plot the World Trade Center and Pentagon attacks.
One suspect who listed a flight school as his address on a pilot's license may have gotten it from printed brochures or the Internet, while online travel sites such as Travelocity were used to purchase tickets.
Attorney General John Ashcroft told Congress that one person in federal custody had downloaded information about crop-dusting planes, which could be used for biological or chemical attacks.
William C. Martel, professor of national security affairs at the Naval War College in Newport, R.I., called online censorship futile.
``We can easily come into the category of shutting down the Internet,'' Martel said. ``Think of how many mundane pieces of information can be used for ill purposes.''
Saying benefits outweigh the potential for misuse, operators of Trip.com kept its FlightTracker service giving real-time information on speed, altitude and location of flights en route.
Boeing, meanwhile, reviewed its Internet offerings the day of the attacks and left everything up. Said Boeing spokesman Bob Jorgensen, ``If it has the potential of aiding and abetting the enemy, it's not out there in the first place.''
AP-NY-10-03-01 1621EDT