Swiss authorities have given Darwin Airline until the end of January to answer more questions about Etihad Airways' plans to buy a third of the Swiss airline before it gives the deal the green light.
Etihad - the national airline of the United Arab Emirates - has already agreed to relinquish a role in the appointment of top executives in order to secure approval for the deal, Darwin said last month.
A spokesman for Switzerland's Federal Office of Civil Aviation (BAZL) said on Saturday that had allayed concerns about Etihad's control of Darwin, but the agency still had questions about the resources Etihad wants to invest in the Swiss airline.
The spokesman did not elaborate on the questions.
Darwin has until the end of January to answer the queries, the spokesman said, adding that the airline had expressed confidence it could provide clarification.
A spokeswoman for Darwin said in an email that the airline would work with Etihad and BAZL to address the concerns.
Asked in October when he thought the deal would be approved, Darwin Chief Executive Maurizio Merlo said: "According to our indications, it should be by the end of this month."
BAZL's extra queries were reported by Swiss newspaper Le Temps on Saturday, which it said was in response to a report by a magazine, Travel Inside.
Etihad plans to acquire a 33.3 percent stake in Darwin, now rebranded Etihad Regional, adding to its portfolio of minority stakes in global airlines.
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