FLUGHAFEN ZÜRICH AG The government launched the tender in May to operate the Balkan country's main airport for 35 years, expecting to bring some 1.2 billion levs (555 million pounds) into state coffers.
Bulgaria already extended the deadline in September due to strong interest in the process.
"There is a big interest among candidates, with more than 900 questions posted to the ministry by potential bidders," the transport ministry spokesman said.
A source close to the matter told Reuters last week that Turkey's Limak Holding, Russia's VTB Capital (>> Bank VTB PAO) and Switzerland's Flughafen Zuerich (>> Flughafen Zuerich AG) would together bid for the operation rights of the airport.
Prior to launching the tender, Bulgarian Transport Minister Ivaylo Moskovski said operators of airports in Lyon, Dublin and London Heathrow, as well as firms from Qatar and China, had also expressed an interest.
The airport, which was used by more than 4 million passengers last year, is currently operated by the state.
The concession procedure was temporarily put on hold following a complaint to the Balkan country's competition watchdog by a consortium that built a runway at one of the terminals. That complaint was rejected in late June.
(Reporting by Angel Krasimirov; Editing by Mark Potter)
