Chennai: Actress Aditi Rao Hydari has been roped in as the leading lady, replacing Sai Pallavi, in ace filmmaker Mani Ratnam's yet-untitled Tamil romantic-drama which also stars Karthi. "Aditi has replaced Sai Pallavi. While the exact reason is still unknown but it's believed that Pallavi had set aside her dates for another project and since this film was getting delayed, she had no other option than to exit," a source from the film's unit told IANS. In the film, Karthi is tipped to be playing a pilot, who falls in love while on his trip to India. The regular shooting is expected to start from June. Double Oscar-winning composer A.R Rahman will compose the tunes, while Ravi Varman will crank the camera.