It was Gerard Brackx who founded the travelcompany in 1971 by the name "Jetair". It used Sabena/Sobelair as carriers to transport the customers to their destinations. In 1996 he sold half of his company to TUI travel and when he gave the company to his son Bart Brackx in 2001 it was completely sold to TUI not much later. Bart Brackx remained in charge of Jetair until he rose to the top of TUI where he became managing director of TUI Western Europe.
AFAIK this month is his last month before he retires at the age of 50 to enjoy life.
JetairFly was founded when Sabena's daughter company Sobelair filed for bankruptcy in 2003/2004, first it was named TUI Airlines Belgium but since the "Jetair" brand is quite big in Belgium (Jetair is the largest touroperator in the country) the airline was rebranded in JetairFly but called by the people "Jetair" like the travelagency. Today Jetair is Belgium's second largest passenger airline and operates as a fully scheduled airliner rather then a charterairline like the other airlines in the TUI Travel group. It's a quite succesful airline today, it has the youngest fleet in the country (nearly all planes are delivered factory new with 6 new planes arriving in 2013). This year the operations of Marrocons TUI airline Jet4you were integrated in JetairFly with all planes now flying on the Belgian register.