No actual plane was involved, but there was a scenario involving a Boeing 767 plane that had been hijacked and forced down at Harare airport.
Not the first time these hijack drills have caused 'panic and anxiety':
Mock hijack drill at Indore airport - Hindustan Times
The Chinese do these drills regularly and publicize them:
People's Daily Online -- Anti-hijack drill conducted in Chongqing
Anti-hijack drill in Nanjing
China conducts anti-hijack drill in Urumqi(21/10/04)