Goedemorgen Pieter, I see you are quite fluent with Vietnamese (not an easy language for Westerners!) I'm pleased to guide you for plane spotting at SGN during weekends. Make sure to bring super telezooms (300mm up) since the locations are always far from the runways and terminals due to security surveillance. AY always use 757's winglet since the beginning in 2008, but I don't think they have normal scheduled flights, probably charter ones since I don't see them coming the past 5 weeks. There is only one flight/week on Saturday coming from Mumbai.