Apple has started to email some customers who ordered their third-generation iPad units on Wednesday, informing them that shipments of their devices will be delayed. Quoting multiple reader reports, MacRumors explains that at least one of these customers was initially quoted delivery on March 16, with others quoted a window of March 16-19. Apple has now pushed back delivery for these customers to March 20 or 21. “Despite our best efforts and those of our shipping partners to get your order to you on time, we want to inform you that [your iPad] will not arrive on its originally scheduled delivery date”, one of the notification emails reads. “Your new delivery date is 20/03/2012.” Apple will officially launch the third-generation iPad in the US, UK, Canada, France, Germany, Switzerland, Japan, Hong Kong, Singapore, and Australia on March 16.