Nonstop air service between Baltimore/Washington International Airport and Jamaica scheduled to begin Feb. 19 is expected to contribute significantly to Jamaica's continuing upswing in tourism, Jamaican government and airline officials said last week.

"We expect this to be one of our major routes in the United States," Air Jamaica Vice President William Rodgers said last week at a luncheon here to announce the new service. The airline initially will offer round-trip service three times a week to Montego Bay using Boeing 727 aircraft, with introductory round-trip fares starting as low as $250.

Noel Mignott, regional manager of the Jamaica Tourist Board, said Jamaica already has seen an upturn in tourism this year. He said that by the end of the winter, the Caribbean island expects tourism from North America to have increased 11 percent over last year. "With this kind of weather, we feel we will be on target," he added.

Increased tourism is an integral part of Jamaican Prime Minister Edward Seaga's plan for the Caribbean island's economic recovery--a plan that has begun to work, according to Keith Johnson, Jamaica's ambassador to the United States.

"Things have calmed down in Jamaica, and we have made some progress in the economy," Johnson said. Out of 500 proposals submitted by U.S. interests to participate in Jamaica's economic development, he said 30 joint ventures already have started up. He predicted that another 100 would be in place by the end of the year.

T. James Truby, BWI administrator, had high hopes for the new flights, the only nonstop service linking the area with Jamaica. "You have a beautiful and warm country," he told Johnson. "We have the nation's fourth-largest and affluent market. We also have a climate that encourages us to leave on occasion. . . ."

While other airlines have faced recession and cutbacks related to the controllers strike, Air Jamaica has been growing as a result of the recent upswing in tourism to Jamaica. Its share of traffic on all its North American routes has increased, airline officials said yesterday.

The airline is owned by the government of Jamaica, with a minority interest held by Air Canada.