The Brazilian airline Azul S.A. (BOVESPA:AZUL4) is working with Citigroup Inc. and Guggenheim Partners as it explores a potential offer for its troubled competitor Gol Linhas Aéreas Inteligentes S.A. (BOVESPA:GOLL4), according to people familiar with the matter. Shares in both companies rallied. The companies are advising Azul as it weighs several options, including an outright acquisition of its rival, one of the people said, asking not to be identified because discussions are still private.

Azul still could decide to shelve the idea, the person added.