AirAsia has already applied to Singapore authorities for an air operator's certificate to fly out of Changi airport and hopes to have the airline up and running by September.It was unclear whether Qantas was considering buying into the planned $US1 billion sharemarket listing of AirAsia in September or a Singapore-based joint venture with the airline, the newspaper said.Qantas chief executive Geoff Dixon last month confirmed it was considering the option of investing in an Asian airline, especially if its proposed alliance with Air New Zealand fell through.However, Qantas public affairs manager Michael Sharp on Thursday refused to comment on the rumours, the Herald said.Singapore Airlines, which this week applied for a licence to fly its own low-cost offshoot, Tiger, said on Thursday it was aware of the rumours.One industry insider told the paper a deal with AirAsia would not only help Qantas's aspirations to enter the South-East Asian market but give it an easy way to phase out its ageing fleet of Boeing 737-300s.AirAsia plans to double its fleet of Boeing 737-300s to 30 by the end of 2004.After flying domestic services in Malaysia since late 2001, AirAsia recently launched services into Thailand and Singapore with its first Indonesian services scheduled for next month.