Do a little research. DL owns 49% of VS. VS isn't in Skyteam mainly because AF/KLM doesn't find they need them to be. There was a time that they were looking to bring VS into the ST fold but that doesn't look like it'll happen. Doing so would likely require DL/VS JV to become part of the overall AF/KLM JV. Not sure VS is willing to do that. Remember VS still is owned 51% by UK holders. In fact they still do codeshares with Singapore Airlines. Also There's little that VS would bring to Skyteam since it doesn't even operate intra-UK much less EU routes. Basically it's all UK/US. The few other countries all have AF/KLM service.