The Falcons’ desire for an open-air stadium “presents a number of complex issues” that are still being sorted out, the head of the Georgia World Congress Center Authority said Wednesday.

The GWCC Authority, the state agency that operates the Georgia Dome, is 14 months into negotiations with the Falcons about a possible new downtown stadium that would be built with a combination of public and private funds.

Speaking at a breakfast event held by the Atlanta chapter of the American Institute of Architects at Ansley Golf Club, and in an interview afterward, GWCC Authority executive director Frank Poe detailed the challenges in finding a stadium solution.

He noted that while the Falcons want to play outdoors, other events that the state and city have no intention of sacrificing — the SEC football championship game, the Chick-fil-A Kickoff game, the Chick-fil-A Bowl and college basketball’s Final Four — “are not going to play outdoors.”

That leads to two options: a dual-stadium setup where the Georgia Dome and a nearby open-air facility would operate in tandem, or a single retractable-roof stadium that accommodates indoor and outdoor events.

Both models remain on the table and both have their own challenges, said Poe, who declined to predict which ultimately will be chosen.

In a dual-stadium model, a deal with the Falcons would need to be structured to ensure the Dome’s long-term viability, Poe said. Among issues that would have to be addressed are whether the open-air stadium could compete with the Dome for scheduling non-Falcons events and whether events could be held simultaneously at both facilities.

“Our [GWCC] campus already is very active, and oh, by the way, we’ve got a major arena [Philips] right across the street,” Poe said. “So when you start trying to peel back the layers of the onion associated with how you make two stadiums work together, the complexity elevates substantially.”

He was asked by an architect in the audience about a one-stadium approach of massively renovating the Dome and installing a retractable roof.

Poe did not rule that out, but he said such an undertaking could close the Dome for two years, forcing Falcons games and other events to temporary homes and costing both the team and the GWCC “a big number” in lost revenue.

As for building a retractable-roof stadium, rather than an open-air stadium, on the nearby site, Poe said: “We’ve always been open that if it needs to be a retractable roof, let’s consider that. We try to keep all of our options on the table, recognizing that sooner rather than later we’re going to have to narrow them.”

He elaborated on the narrowing process: “Is it one or two [stadiums]? And [what’s] the location and the cost? And then you start getting into sort of the structure of the deal.”

The Falcons have stated a preference for an open-air stadium, but have not ruled out other options.

“I know [the Falcons] are working aggressively to get to a point where they can come back and say, ‘This is the path we want to be on,’” Poe said.

He declined to discuss a timetable for a deal, in part because he’s not sure his would be the same as the Falcons’.

The Georgia Legislature two years ago agreed to extend Atlanta’s hotel-motel occupancy tax from 2020 to 2050 as a funding mechanism for a new or renovated stadium on GWCC property. Poe said the hotel-motel tax “is the only source of public revenue” to support a stadium project.

“Assume for purposes of discussion that is about a $300 million contribution,” he said, adding that a 2011 study put the cost of an open-air stadium at $700 million. “Who makes up the balance? Well, the team makes up the balance.”

He said NFL teams are “a hot commodity from a financing perspective” and their future revenues are “extremely bankable.”