The airline and railroads - which really haven't gotten along since the 1930s when plane passengers would "fly by day and take the train at night" - are renewing old ties.

Eastern Airlines and Auto-Train have teamed up to offer a series of travel packages from the East and Midwest to Florida. Vacationers will be transported by plane, while their autos will travel by train. The two transportation companies are so sure of the success of the project that they're already accepting reservations, although the first trip is not scheduled until the middled of October and approval is required from the Interstate Commerce Commission.

Under the plan, vacationers will have reserved space for their cars on the Auto-Train system between the terminals of Lorton, Va. (15 miles south of Washington, D.C.), and Sanford, Fla. (near Orlando and Disney World), or between Louisville, Ky., and Sanford.

(In June, Auto-Train was designated the "official family railroad of Walt Disney World" and is sponsoring the WDW railroad at the Magic Kingdom. The company will be represented at the reservations desks at both the Polynesian and Contemporary Hotels there.)

After dropping off their cars at the Auto-Train terminals, the travelers are offered several options. From Lorton, for instance, they'll get free transportation to Washington National Airport where they can board an Eastern flight to Orlando. In Orlando, they'll be driven to a hotel to spend the night, and the next morning taken the 21 miles to Sanford to pick up their car. Not including airfare, the packages costs $109.40 per adult, double occupancy.

Similar packages are available from Louisville, and are priced from $104.50, excluding air fare. And return trips work the same way. Eastern and Auto-Train are high on the concept, even though planes and trains are in open competition for the passenger dollar.

"I think we'll both benefit greatly by the plan, said David Kunstler, Eastern vice president. "We think we'll be giving the traveling public something they've been wanting for a long time." Richard Goldstein, Auto-Train vice president, also feels the partnership will be a beneficial one. He explained that Auto-Train missed business, especially during peak seasons, because they do not have enough passenger cars. "We had too many passengers and couldn't accommodate them all, though we have enough trains to carry the automobiles. Under this plan, we'll be able to carry passengers as well as the cars of Eastern's passengers."

If the plan is approved and proves popular with the public, it may usher in a whole new concept in vacation travel. Eventually we may see trains transporting automobiles from every major city, while their drivers are flying to the same destinations. It not only would cut down wear and tear on both driver and car, but also in these days of the fuel crunch could prove to be an enery-efficient combination as well as an economically pratical one for the long-distance motorist.