Unable to connect via wireless and landline phones, many New Yorkers posted messages on Web sites, signed on to instant chat services, and used e-mail to contact loved ones.
"There is no phone service in or out of Manhattan, so e-mail is the way to communicate. We are OK," read one e-mail message a worker in New York's Equitable building sent to friends and relatives.
"The WTC is just 10 blocks above, and we all saw EVERYTHING happen as it unfolded," wrote another New York City worker. "We are all in shock. It is hard to work. We are also trapped into the city; we can not get home."
Some concerned New Yorkers even set up personal Web sites to have friends and family check in with each other and verify each other's well being. Bill Shun built a Web log asking friends and family from New York City and other affected cities to sign in showing that they were OK.
One New York resident who couldn't get to traditional news sources over a T-1 line jumped onto IRC (Internet Relay Chat), to find footage of the plane crashes and get information on the events.
"Normal Web/Net paths are overloaded...IRC has always been a good source of information when something like this happens...(It's) sort of a 'backdoor' to the rest of the Internet," said one New York-based IT manager who went by the handle "Man in Black." He said he found some good information about the events and "some rumors flying, of course, but I try to keep a level head."
He was joined by thousands using chat rooms to exchange information on the attacks. Already people have set up discussion groups using IRC under "Worldtradecenter," "Wtc" and "Terrorist-moderated."
IM services from Yahoo and America Online experienced increased demand as people sought to contact friends and family. A Yahoo representative said the company's network had experienced "an unprecedented increase in traffic" and had added more servers to handle the load. AOL said that it had seen a "small spike" in instant chat usage.
Web communities also bubbled up all over the Net to let people comfort one another and get information. People on Yahoo Groups created a public discussion group to share information on the attacks. Craig's List, an international community listing of jobs and related information, created an open forum on the disaster.
Others worried about false tips, and terrorist propaganda shut down a service called "remailing" that allows people to cloak their identity when posting to Internet sites and newsletters. One such service, called Randseed, was taken offline as "a precautionary measure," according to an e-mail from its operator, to thwart bogus threats or tips from anonymous senders. Remail services allow those who want to maintain their privacy online to anonymously send e-mail by bouncing it through several servers.
Businesses located in and around the World Trade Center also used the Internet to provide updates on the status of their operations.
The Marriott Hotel posted this notice on its Web site about its 800-room hotel at the World Trade Center: "The hotel has been evacuated. We are working closely with authorities and they are managing the situation. We will continue to monitor and provide updates as we have new information. We are activating a special number for inquiries, and it will be available soon."
The American Red Cross used the Internet to reach out for help, asking technology companies to donate Web advertising space to urge people to donate blood. Among the contact information given in the ads were 1-800-HELP NOW to reach the Red Cross and 1-800-GIVE LIFE for donating blood.
Morgan Stanley, headquartered in the World Trade Center, also posted a notice on its site about the collapse.
The law firm of Sidley Austin Brown and Wood, which has its New York office in the World Trade Center, used its Web site to let clients and employees' families know that it believed its workers were evacuated safely.
"Due to the tragic events that have occurred in New York and Washington this morning, we are closing all of our offices. We will keep you apprised of developments, as appropriate, via the Web site, voice mail and e-mails. Based on the information currently available to us, we understand that all of our personnel in the World Trade Center were evacuated safely."
The rush to find alternative modes of communication was partially the result of the loss of cell phone service in much of New York City after the attack.
Frank Davis had been trying to reach his wife, who left him a voice mail after getting out of a subway in Manhattan's financial district just a few minutes after the first plane struck.
Although she "sounded fine--just shaken," Davis said he had yet to reach her.
"Nothing has worked since about 9:15 a.m. (EDT), and it still isn't working," he said in an e-mail to CNET News.com. "I've been trying pretty much every 10 minutes."
Some cell-phone carriers asked customers to use alternative methods to communicate.
VoiceStream Wireless, for example, asked customers to use short text messaging, which is similar to sending instant messages on PCs. Such messages are sent over a different network so they don't clog the ones used for voice calls or emergencies, a VoiceStream spokeswoman explained.
Still, e-mail seemed to be the preferred communication tool.
Gartner analysts Maurene Grey, Joyce Graff and Robert Batchelder say the Internet forms the lifeline for business communications--one that may
work when others do not.
"It's just been impossible to get through on the phone lines this morning," Walker said. "So I've been sending e-mails to friends and family, letting them know what I know, trying to understand what's going on, making sure everything is OK."
He noted that many of the major news outlets on the Internet were unavailable when he tried to get further information on the attacks.
Tony Borelli, a senior writer for New York-based human resources consulting firm The Empower Group, sent e-mail to "everybody I could think of" after the attacks.
Borelli, who could see one of the towers from his office near the United Nations, said he sent out the e-mails "as soon as things got really bad because I knew people would worry about me. After that, the e-mails I got were from people worried about other folks in Manhattan, and news updates.
"We were at a window in our office on East 45th Street, watching the one twin tower burning. Then we walked away for a while. Then we came back, and the tower was gone, and there was just a huge volume of smoke in its place," he wrote in the e-mail.
"Now we're milling around, watching fighter planes roaring overhead, wondering how we're going to get off this island. All the bridges and tunnels and trains and airports are closed down. As I write this, the second twin tower has now collapsed."
CNET News.com's Margaret Kane, Ben Charny and Ian Fried contributed to this report.