At the same time, online companies such as Amazon.com, Yahoo and PayPal did their part to help out in relief efforts, allowing companies to make online payments directly to the Red Cross.
Perhaps most affected by the disasters were the online travel sites. With air traffic halted nationwide and thousands of flights cancelled, such sites saw transactions slowed down and customer service centres swamped with calls.
Because the Federal Aviation Administration has yet to lift the ban on air traffic, Priceline.com, which gets much of its business from last-minute travellers, has stopped taking new reservations through this Sunday, company spokesman Brian Ek said. Ek declined to say how that had affected the company's business, but Priceline gets more than 90 percent of its revenue from travel-related sales.
For customers already holding tickets, Priceline is directing them to first contact the airlines directly about refunds and cancellations.
"If for any reason you can't make it to your destination, call and we'll work with you," Ek said. "We're going to abide by what the airlines decide to do," Ek said.
Competing airline site Expedia also is getting lots of calls, and has stopped taking reservations for flights departing before September 18.
Spokeswoman Suzi LeVine said Expedia will try to help customers cancel tickets or get refunds even for tickets that previously could not be cancelled.
Orbitz is continuing to take reservations, but there are few takers.
"Less people are buying online in general and I think that's also true for brick-and-mortar goods and services as well," said Stacey Spencer, an Orbitz spokeswoman.
Grounding the nation's planes has also stalled deliveries for online businesses and auction houses. Air cargo comprises about 40 percent of the value of world trade and e-commerce companies depend on it for shipments both from their suppliers and to their customers.
Online auction giant eBay warned members of Post Office closures and possible delays in receiving packages. Etail leader Amazon.com said that while it doesn't expect the groundings to affect the shipments it receives from suppliers, they will delay overnight deliveries to customers.
Meanwhile, package delivery giant UPS warned customers on its Web site that the bombings would cause some delays throughout the country for an indefinite time.
As package delivery slowed, so too did some online transactions. At the same time, many Web sites turned over large amounts of space to urge people to donate to the Red Cross. By midday Wednesday, Amazon customers had donated nearly nearly US$800,000 to the Red Cross through Amazon's online payment system. Several other online companies set up similar payment systems, such as PayPal and Yahoo. The Red Cross also directed some visitors to Helping.org, a nonprofit group set up by Internet and media giant AOL Time Warner, that lets people make online donations to a variety of charities.
Some online auction sellers apparently attempted to cash in on the disaster, listing World Trade Center and Osama bin Laden-related items on eBay and Yahoo's auction site. A search for "World Trade Centre" on eBay, for instance, turned up 47 postcards, t-shirts, newspapers and other items. A similar search on Yahoo revealed 5 items.
eBay quickly announced that it had banned the sale of items with any words that reference World Trade and Pentagon until Oct. 1, and most of the auctions were cancelled.
And on Amazon, books related to the World Trade Center Twin Towers or terrorism jumped to the top of the company's best-seller list. The No. 1 seller on Amazon was "Twin Towers: The Life of New York City's World Trade Centre," according to Patty Smith, an Amazon spokeswoman.
Also among the top 10 sellers was "The New Jackals: Ramzi Yousef, Osama bin Laden and the Future of Terrorism," a biography of the men who allegedly masterminded the 1993 bombing of World Trade Center.
"Anytime you have a major news event, sales of books with anything to do with the subject skyrocket," Smith said.
CNET News.com reporter Margaret Kane and Reuters contributed to this article.
