Task: Question Generation
Input (English): Context : South African Airways Flight 228 was a scheduled flight of the Boeing 707-300C Pretoria, registration ZS-EUW, on 20 April 1968 from Johannesburg to Heathrow via Windhoek, Luanda, Las Palmas and Frankfurt. 
Subject : South African Airways Flight 228 
Relation : point in time
Output (English): What was the date of South African Airways Flight 228?