Royal Caribbean Cruise Line's earnings were significantly down in 1991, according to a prospectus filed by the company for a $100 million bond offering.

Last year, RCCL earned $43 million on revenues of $760 million, compared to $52 million on revenues of $698 million in 1990.

The document, filed under the name of RA Holdings with the Securities and Exchange Commission, said that the $963 million expected from the sale of the notes would be used to repay debts as well as for general corporate needs.

In 1991, operating expenses were up 19 percent, from $407 million in 1990 to $484.4 million in 1991. While operating expenses accounted for 583 percent of the total revenues in 1990, they increased to 63.8 percent in 1991.

Since 1987, the line has spent $1.1 billion to expand and enhance its fleet and meanwhile tripled its capacity from 4,150 berths in 1987 to 14,280 in 1992. By incurring long-term debt of $1.25 billion, the company is more highly leveraged than a number of its competitors.

Revenues steadily increased from $364 million in '87 to $760 million in '92 and net income also increased from $36 million in '87 to $52 million in '90 until the drop to $4.3 million in 1991.

Reasons for the decreased net income are: the Gulf War; recession; increase of marketing costs due to fleet expansion; increased agency commissions "due to additional incentives relating to the softer market"; increases in airfare; and the delivery delay of the Monarch of the Seas.

Overall, RCCL saw a four percent decrease in revenue per berth in 1991.