Computers--already busily cranking out airline and other carrier schedules, storing booking data for all manner of trips and taking care of the billing -- are now entering a new phase that could be revolutionary for the U.S. travel industry and the traveling public.

Norwegian American Cruises has announced it has become the first cruise line to sell its voyages via computers directly to owners of home computers and computer terminals.

"We all know that computers are the marketing and communications tools of the future and NAC is always interested in exploring innovative means" of booking its cruises, said Michael Grossman, the cruise line's vice president of marketing. "We are pleased that we will be testing a program of cruise promotion via computer with the world's largest privately owned commercially operated 'videotex' service," CompuServe Information Services.

Initially, according to NAC, the computer has stored data on the Sagafjord's four-night samplers from Los Angeles, departing June 5, June 9 and June 15, and the series of five Alaska/Canada itineraries leaving San Francisco June 19, July 3, July 17, July 31 and Aug. 14. CompuServe subscribers can now call a toll-free number to buy a cruise--thus bypassing the travel agent.

While this very limited experiment does not signal the demise of the professional-agent system of marketing travel, it is certainly not being viewed with unalloyed pleasure by agency personnel. One of the worst nightmares of some agents has involved what they perceive during waking hours as the potential long-range threat from computers. Tourists and business travelers already have the option, in most cases, of dealing directly with airlines, ship lines, hotels, etc., often by using a toll-free phone number; but that is considerably different from being able to call up an entire current flight or cruise schedule, a detailed list of tour packages, and descriptions of selected resorts on a computer screen in your home or office, compare the latest prices, and then make your choice on your own keyboard.

Of course, much would depend upon how much information has been entered in the computer and how easily it could be used, since this method does not permit a face-to-face exchange and you can't get instant answers to questions.

Travel agents pride themselves on offering individual service to their clients--and Bob Loewenthal, chairman of the American Society of Travel Agents' maritime committee, said he did not personally believe that silicon chips would ever be a satisfactory substitute.

"Only the travel agent can provide the full service required," maintained Loewenthal, who was contacted at his agency in Fort Lauderdale, Fla. "Consumers will become disappointed with the gap between the computer system and their requirements." Loewenthal added that ASTA's formal response to the NAC move would be discussed at the next regular meeting of his committee. ASTA represents more than 10,000 U.S. and Canadian agents.

Grossman of Norwegian American Cruises, also interviewed by phone, saw no cause for agents to be upset by his experiment. "They would be concerned without reason," he said, adding that "we're protecting agents' commissions"--subscribers booking cruises by CompuServe will be asked the name of their agents (if they have them) so that NAC can pay the commission.

"Our product, deluxe cruising, happens to be particularly complicated," Grossman said, adding that he thought clients who were not familiar with the ports of call, the ships, the multiple decks and the types of staterooms would still need the advice of an agent. Thus, he said, the computer would act "as a stimulus." He agreed that in the case of certain regular short cruises, there is "a greater likelihood" agents might not be consulted.

NAC, which operates the liners Sagafjord and Vistafjord, is an upscale cruise line with other sailings to the Caribbean, Trans-Panama, Mediterranean, Scandinavia, transatlantic, India/Africa, China/Orient, South Pacific/South America and an annual world cruise. Its two vessels earned the top rating, "Five-Plus Stars," from "Fielding's Worldwide Guide to Cruises"; the World Ocean & Cruise Liner Society named the Sagafjord "Ship of the Year" for '82, and Garth's "Profile of Ships" picked the Vistafjord as "Number One Ship Afloat."

CompuServe, which has more than 45,000 subscribers around the country, gives users access to a variety of information services in such fields as electronic shopping and banking, stock and commodities markets, electronic mail, family education, travel, games and news. It can be used with all popular makes of personal computers and many computer terminals.

NAC is not the first travel-related firm to sign up with CompuServe--the Official Airline Guide (with schedules of all domestic and foreign flights), Pan Am's Travel Guide (information on foreign destinations), and Worldwide Exchanges (a directory of vacation homes and yachts listed on an exchange basis) are among those also available.

Interestingly, two full-service travel agencies have joined the CompuServe network to display their products to consumers on computer screens--instead of only in their offices--and book trips by air, rail and steamship. First World Travel of Coronado, Calif., an ASTA-member franchise company with 50 syndicated agencies in this country, has a 24-hour retail operation at its Coronado headquarters, which will move to the Los Angeles Airport in June.

"We service all the CompuServe subscribers, who can pull up all our tours and cruises," said Jeff Flanagan, First World's sales vice president. They can also get "domestic and international documentation and airline tickets."

"This is going to be one way the public will be buying their travel," said Dave Hancock, executive vice president, adding that "there will still be the personal service" given by retail agencies. Hancock explained that with the on-line computer operation, a subscriber can look over his company's tour packages, for example, type a request for further information 24 hours a day, and an agent ("not just an information clerk") will research the request and send a reply by electronic mail, which will arrive overnight or earlier.

Another agency servicing clients via CompuServe is Travel America, a wholly owned subsidiary of Andromeda Information Systems of Englewood, Colo. Travel America, acting as an outside sales agency for the Sheridan Travel Agency in Denver, also an ASTA member, is currently booking tours and cruises and providing other travel information. Purchases are charged to credit cards and tickets are mailed or can be picked up at airport counters.

"It's an opportunity for us to look toward the future, to help shape it," said Sheridan manager Tom Jensen, "not to wait until it's too late."