Auto-Train Corp. yesterday reported its biggest quarterly loss ever, a $1,592,000 deficit for the three months ended Sept. 30, which represent the slowest season for travel on the company's route between Lorton, Va. and Florida.

In another earnings report, Woodward & Lothrop profits were off sharply to $2,129,000 (88 cents per share) from $2,935,000 ($1.18 per share) despite a 5.3 percent increase in sales to $64.8 million from $60.5 million.

Auto-Train President Eugene K. Garfield blamed his company's "disappointing summer" on new discount air fares on Florida routes that went into effect just as Auto-Train was raising its prices.

"The company could not respond in time to those competitive pressures," said Garfield, whose railroad has had rough going for the past three years.

Auto-Train lost just under $1 million in the same three months a year ago, but the company has changed its fiscal year so a precise quarter to quarter comparison is difficult. For the three months ended Oct. 31 last year, Auto-Train lost $1.1 million on revenues of $6 million. This year revenues were $4.3 million.

Garfield said the company "has achieved major reductions in its general and administrative expenses and has made significant progress in its previously announced plan to restructure its debt."

One of the line's major lenders, American Security Bank, has agreed to let Auto-Train pay only the interest on a $3 million loan for three years and to extend the maturity of the loan from two years to five years. Garfield said the company hopes to obtain about $600,000 in new financing.

Woodward & Lothrop said sales of its department stores increased 7.1 percent for the quarter ended Oct. 31 to $64.7 million from $60.5 million. But Chairman Edwin K. Hoffman said, "Sales on a store-for-store basis for the quarter have not been keeping pace with the increased costs of doing business."

In addition to opening its 14th store, at Lakeforest Mall in Gaithersburg, during the quarter, Woodies completed renovation of its Chevy Chase store and continued its major remodeling of its downtown store.

For the first nine months of its fiscal year Woodward & Lothrop's earnings declined to $5.4 million (2.23 per share) from $5.9 million ($2.44), as sales increased 5.3 percent, to $178 million from $169 million.