On 2 August 2007, a Fokker F50 on an ILS approach to Maastricht in IMC came into close proximity inside the CTZ with an unseen light aircraft which had failed to comply with its Special VFR transit clearance. The Investigation found that the transiting aircraft had come within 0.14nm / 260 metres of the opposite direction F50 at a similar altitude without either aircraft having sight of the other, and that the Harvard had been wrongly assumed by ATC to be a helicopter after an initial lack of call sign prefix clarity on first contact had not been positively resolved.