February 23, 1984

Plans are under way for direct private bus service between lower Manhattan and the metropolitan area's three major airports. There is no direct airport bus service now to the busy financial and government center. Within three months, Carey Transportation plans to link downtown Manhattan with at least one of New York City's two airports, using vans or full- size buses. Carey had run an indirect downtown service for a short time, but it was stopped in 1982.

Ten years ago Lydia Bragger was the scourge of Madison Avenue. Whether she was speaking before the National Association of Broadcasters or the House Committee on Aging, she complained about ''ageism'' in advertising and ''the negative images and stereotypes that make old people look sick and bothersome and boring.'' Nowadays the 80-year-old head of the Gray Panthers Media Watch, an organization that fights discrimination against older people, is much in demand as a consultant to advertising agencies that are starting to tailor some ad campaigns to attract consumers over 55. More manufacturers are also adapting their products and marketing strategies to this age group. And with good reason.

The 17-year-old son of the Pelham Village Fire Chief was found hanged in his family's home Tuesday, the police said today. It was the fourth teen-age suicide in Westchester and Putnam Counties in the last two and a half weeks. Two of the other youths hanged themselves, and a third died from a gunshot wound. Word of the latest death brought reactions of shock from many parents and teen-agers in the suburbs. Westchester County officials said there were three teen-age suicides in the county in 1982 and two in 1983.

The Supreme Court, in a victory for the Internal Revenue Service, curbed a popular tax-avoidance device today by ruling that an interest-free loan from one family member to another is subject to the Federal gift tax. The Court said that the value of such a ''gift'' is the interest that has not been charged. The 7-to-2 ruling did not indicate how the interest should be calculated. But by any calculation, the forgone interest would have to be substantial before incurring the gift tax. Tax must be paid only on gifts to any individual in one year that exceed $10,000. For a married couple, the exclusion is $20,000 for each recipient.

THEY work in wood and metal, concrete and plastic laminate. They make tables and chairs and storage units. Their styles range from traditional to Art Deco-inspired to the more brash and colorful shapes influenced by the Milan- based Memphis group of designers. A new breed of modern furniture designer is emerging: young artists and craftsmen who often refer to their work as ''functional art'' and who offer a special kind of custom furniture. Although their work is not inexpensive, many of the pieces solve everyday furnishing needs while remaining true to the the esthetic ideals of their makers. Most of these designers, working in lofts and studios, are available only by telephone appointment.