The average total cost for a business traveler's domestic car rental in June was flat year-over-year at $217.13, according to the National America Business Travel Monitor.

The report covered travel data for the first half of 2010, including details of trends in U.S. domestic and international airfare and hotel rates paid by business travelers this year.

The report also showed that the daily cost to rent a car in the United States was $71 in June, down 1 percent from May and up 2 percent compared to the year-ago period.

Meanwhile, the distribution of cars among rental companies remained flat for June. Intermediate-sized vehicles accounted for the majority of all rentals, with 59 percent of the total. Full-size vehicles accounted for 20 percent; sub-compact/compact vehicles were 19 percent and luxury/sport vans were 2 percent.

The average length of rental in June was 3.06 days, down 2 percent year-over-year.

The report also found that overall airfares have increased substantially versus the first half of 2009, climbing steadily towards pre-recession levels as of June 2010. However, hotel rates have decreased slightly compared to the first half of 2009, but rate changes have varied dramatically based on region. The report said that hotel price declines are likely to cease and will even begin to rise in the 2011 negotiating season.

"The travel marketplace continues to change quickly as recovery occurs, creating new challenges for both travel managers and business travelers who became accustomed to significant discounts during the recession," said Christa Degnan Manning of American Express Business Travel.

"Airlines took many steps to position themselves for survival over the past 18 months to strengthen themselves and drive revenues and profitability. With travelers on the road again, air suppliers have gained ground in pricing power and the end of hotel rate drops is likely near. This means companies have to reconsider contracts, policies, and cost-savings tactics that may no longer be relevant," she said.

The report was conducted by American Express Business Travel, a provider of business travel management.