The projected cost of a new tramway and rental car center for Hartsfield-Jackson Atlanta International Airport has increased as much as 30 percent, leading the city council to seek an outside auditor to find out what happened, The Atlanta Journal-Constitution reports.

Two years ago, airport General Manager Ben DeCosta told the council, which oversees the city-owned airport, that the consolidated rental car facility would cost about $211 million, including the elevated tram that will connect with the airport on the other side of the I-85 freeway.

Costs have now risen to about $235 million, and the price could hit $275 million after final construction contracts are approved, DeCosta said.

The rental car facility was scheduled to open in December 2008. The facility, which will replace rental car operations inside the airport, is now slated for a 2009 opening.

According to The Atlanta Journal-Constitution, Councilwoman Felicia Moore called for the audit last week after DeCosta told the Finance Committee that he probably will need more money. DeCosta said he expects to file a request for up to $40 million by Labor Day.

Part of the auditor's job will be to review the airport's construction practices to determine whether they are the best way to get a job done, Moore said.