After attending college at the Royal Cadets School in Laeken (BE), he was recruited by the Belgium Air Force as a student-pilot in October 1974.

Upon completion of his training on Marchetti, Fouga Magister and T-33, he received his wings on 17th of February 1977.

He was assigned to 23 Sqn in Kleine Brogel, flying Starfighter F104G.

In 1981, he completed his conversion to F-16.

After completing his operations officer tour, he attended the superior officer course at the Royal Defence Institute.

In 1988, he was promoted to Major and assigned to represent the Belgian Air Force as an F-16 demonstration pilot for the next 3 years flying at national and international air shows.

From 1990 until 1992, he joined the Flight Safety section of the Belgian Air Force.

On completion of this tour of duty he returned to Kleine Brogel as commanding officer of 23 Sqn.

In 1995, he was promoted to Lieutenant Colonel and assumed the function of Wing Flight Safety Officer.

In 1996, he was transferred to Headquarters Allied Forces Central Europe (AFCENT) at Brunssum (NL) to become the Training and Evaluation Officer.

In 1999, he continued his international career on the Reaction Forces Air Staff at Kalkar (GE).

On 27th September 2001, he was appointed as 21st Corps Commander of Koksijde AFB. In addition to his command duties he performed SAR missions on the Sea King.

He was promoted to Colonel on 26th December 2002.

Colonel De Decker was appointed to his present position as Division Head A1 (Manpower and Personnel) at CC-Air HQ Ramstein (GE) on 25th October 2004.