Despite a rebound in travel, there simply isn't much to like about Dollar Thrifty Automotive Group (NYSE:DTG). The rental car operator owns two of the more prominent names in the industry, with 820 offices throughout North America (two-thirds of which are operated by franchisees). Recent acquisitions at Dollar Thrifty may be driving revenues to record highs, but very little ever seems to find the bottom line. Last year, revenues grew 8% to $1.3 billion, while net income fell 58% to $19 million.

At first glance, first-quarter numbers released this morning look encouraging. Revenue growth was again substantial, leaping 19% to $298 million, with net income climbing from $0.02 to $0.25. Over half of the gain, however, was the result of a change in accounting practices. Excluding this, earnings per share of $0.11 weren't even within shouting distance of the $0.29 estimate. Furthermore, revenues per day declined marginally, and vehicle leasing (which last year accounted for 15% of total revenues) fell 52% to $17.8 million.

Taken alone, last quarter's net profit margin of less than 1% is sufficient cause for concern, but other problems abound. With a debt-to-equity ratio approaching five and more than $2.5 billion in long-term debt, the balance sheet is in disarray. Dollar Thrifty's interest coverage of 1.4% trails both the industry's 4%, and the broader S&P 500's 11.5%.

Capital expenditures as a percentage of sales have been running on the order of 300%, placing positive free cash flow light years away. Valuation isn't attractive either: The stock currently trades at a P/E of 35.

To be fair, a few bright spots could be gleaned from today's earnings. Vehicle rental revenues were up 33.8%. Also, acquisitions expected to close next month will increase Dollar Thrifty's 85,000 vehicle fleet by 7,000. By comparison, Ford Motor's (NYSE:F) industry-leading Hertz operates some 525,000 vehicles. Nevertheless, until substantial debt reductions and margin expansions are evident, I would steer clear of this one.

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Fool contributor Nathan Slaughter can decipher financial statements, but not itemized rental car bills. He owns none of the shares mentioned.