On 2 August 2007, a Fokker F50 being operated by KLM Cityhopper making a daylight ILS approach in IMC to Maastricht on a scheduled passenger flight came into close proximity inside the CTZ with a privately operated North American T6 Harvard which had failed to follow its clearance to enter the CTZ. The initial R/T contact by the T6 to Maastrict ATC had been difficult to make out and resulted in ATC believing that the traffic was a helicopter rather than a fixed wing aircraft