The two have signed a deal that will let FAX use the AirAsia brand.
Service is expected to begin in July and focus on destinations more than four hours away from Malaysia's capital, Kuala Lumpur.
Destinations being considered include Tianjin in China, Amritsar in India and Manchester in Britain. Australia may also feature on the list later, AirAsia said on Friday.
Abdullah Ahmad Badawi, the Malaysian prime minister, said the launch of AirAsia X would bring people from around the world closer.
"What was seen to be an elitist form of transport became a facility that people could afford. People who previously were not seen as potential passengers were able to fly," he said.
AirAsia will not be directly involved in the long-haul project's operations, but leading executives at AirAsia are FAX's main shareholders. Kamarudin Meranum, AirAsia's executive director, has a 20 per cent stake in the privately held company, while Fernandes owns 10 per cent.
Raja Azmi, who has a 20 per cent share, has stepped down as AirAsia's chief financial officer to become AirAsia X's chief executive.
Local media reported this week that AirAsia might team up with Britain's easyJet and the Virgin group to create a long-haul airline.
The tie-up would have given AirAsia access to London's Stansted airport and Virgin and easyJet access to Kuala Lumpur's low-cost terminal.
AirAsia said on Friday that there had been discussions with easyJet and Virgin but no deal had been struck. AirAsia X expects to buy 20 aircraft in January - either the Boeing 777-300 or the Airbus 330-300.
Meanwhile, AirAsia is looking to double its fleet of 50 commercial jets by 2012. It has firm orders for 100 Airbus A320 aircraft, with options on 30 more.