Republic Airways Holdings Inc. said Tuesday that it was extending exclusive negotiations with a potential buyer of Frontier Airlines for two weeks, until Sept. 30.
Republic said the two sides were making progress and trying to tie up remaining unsettled conditions in a July term sheet.
The company has not publicly identified the bidder. Numerous published reports have identified it as former Spirit Airlines Inc. Chairman Bill Franke's investment firm, Indigo Partners LLC. Spirit is a low-fare carrier that relies heavily on low costs and charging customers fees for specific services.
Republic announced the extension as shareholders met in New York.
"Sitting here today, we have made substantial progress toward reaching a definitive agreement with the buyer," said Republic Chairman and CEO Bryan Bedford, "and while we can make no assurances, we believe providing the additional time will allow for the process to be completed."
Indianapolis-based Republic, which operates regional-airline service for bigger carriers such as United and Delta, announced in July that it had reached an exclusive but nonbinding agreement with a potential buyer for Frontier, which it bought out of bankruptcy.
Republic shares rose 38 cents, or 3.1 percent, to $12.54 in late morning trading. Through Monday's close, they had more than doubled in 2013.