Standard & Poor's Ratings Services recently assigned a "B+" corporate credit rating to car rental company Dollar Thrifty Automotive Group Inc., the Associated Press reports.

A "B+" corporate credit rating is non-investment grade and indicates that the company's financial situation varies. The outlook on the rating is stable, meaning that it is unlikely to change.

In addition, S&P assigned a "BB-" rating to Dollar Thrifty's proposed $600 million secured credit facility. The ratings service assigned a "1" recovery rating, due to its high expectation of full recovery of principal if there is a payment default.

S&P also noted that Dollar Thrifty is less geographically diverse than its major competitors. Also, the company generates 90 percent of revenues from airport locations.

"Demand tends to be cyclical, and can also be affected by global events such as wars, terrorism, and disease outbreaks," the ratings service said.

According to the AP, S&P said the outlook could be revised to negative if the company implements a substantial share repurchase program.

Dollar Thrifty shares fell 69 cents to $48.20 in afternoon trading.