For at least two prominent insurance companies,the Sept. 11 terror attacks will hit produce a greater loss on the investment side than on the insurance side.

Prudential Financial Inc. and Principal Financial Group Inc. said that policy claims from the terrorist attacks may actually wind up less than potential investment losses from the $4.7 billion of airline, hotel and insurance bonds that the firms hold, according to published accounts. This is because the value of bonds issued by travel-related companies has plummeted since the attacks as more and more airplane seats and hotel rooms go unoccupied.

Principal said it held $953.2 million of bonds issued by companies affected by the terrorist attacks, including $508.5 million of airline bonds, some of which are secured by jets. It had $172.1 million of hotel and gaming company debt. Prudential said it owned $3.7 billion of debt from airlines, insurers, or travel and hotel companies that could be hurt by the terrorist attacks.

Although these holdings only account for less than 4 percent of each of the two companies’ travel-related holdings, a 5 percent decline in the value of bonds affected by the terrorist attacks would reportedly still create losses at Prudential and Principal exceeding the cost of policy claims.