The Indianapolis Airport Authority announced late Monday afternoon that CEO John D. Clark III has stepped down, effective immediately.

Recently appointed airport board president Mike Wells said the parting of ways came after he and Clark met Monday afternoon "to discuss how we were going to go forward and whether we were going to go forward."

He said the two met because a three-year letter of intent Clark signed when he joined the aiport was set to expire soon. He said Clark had worked under a letter of intent, never a formal contract. Wells said he was not sure why that was the case.

Asked whether he had been happy with Clark's performance or whether Clark's large expenditures on travel were a factor in his departure, Wells said: "It's a personnel matter. Our policy is not to discuss those things."

The sudden departure comes just two weeks after IBJ reported that Clark and two key officers spent more than $67,000 last year on travel that included extended trips to Brazil, Denmark, Greece, Morocco and Switzerland.

In that article, Wells said he planned to tighten oversight of executives' travel. He conceded that he could be perceived by airport executives as micromanaging.

"If so, so be it," said Wells, who was appointed to the post by Mayor Greg Ballard. "I'm probably not going to win homecoming king at the airport."

WXIN-TV Channel 59, IBJ's newsgathering partner, reported late Monday afternoon that Ballard was unhappy with the pace of economic development at the airport.

"I think that’s been slow, much slower than I would have expected," Ballard told the station.

"It may have been the recession. It may have been all the economic downturn but I want to have more plans for development out there. That’s what I’m mostly focused on."

Airport officials said Robert Duncan, a longtime airport executive who retired last year, has been named interim director, pending approval of the authority's board, which meets Friday.

Duncan would hold the position until a search for Clark’s successor has been completed, according to a press release from the authority, which manages the airport.

“We thank John for his service during a period of turbulence in the aviation industry,” Wells said in a prepared statement. “Despite these challenges, we believe that there is a great opportunity ahead for the Indianapolis International Airport.”

Clark, 51, was not immediately available for comment.

In a prepared statement distributed by the airport authority, Clark said: “I want to thank my team of fellow IAA employees; together, we accomplished a lot over the past three years. An airport is one of the most powerful economic development engines a region can have, and from day one we have worked to position the Indianapolis International Airport for long-term growth and success.”

In IBJ's article on airport executives' travel earlier this month, Clark had defended the overseas trips, saying they helped management learn best practices. He pointed out that the airport spent less than three-tenths of 1 percent of its operating expenses on travel and related expenses in 2011.

WXIN reported on Clark’s travel expenses late last year. Michael Stayton, the airport authority president at the time, told the station that he had personally reviewed Clark’s travel expenditures and had no problem with them.

Technically, money spent on airport executives' air travel does not come from tax dollars. Clark said in a statement he provided for IBJ's March 10 article that travel expenses are funded entirely by revenue from airlines, which comes in the form of landing fees and space rentals.

Airlines "have praised the IAA for its fiscal management and commitment to lowering airline costs even as they are increasing at many airports," he said in the statement.

Clark came to Indianapolis from the Jacksonville, Fla., airport, where his travel expenses also had generated controversy.