The Wall Street Journal reports that Apple has told its suppliers to prepare to build a record number of next-gen iPhones. According to the Journal, Apple is looking to produce 70-80 million units by December 30th. As reported earlier this month, both the 4.7-inch and the larger 5.5-inch models of the upcoming iPhone are expected to enter mass production in the coming weeks.

This is a big jump from the previous iPhone models. Last year the company only ordered 50-60 million of the iPhone 5s and 5c. Manufacturing parter Foxconn recently hired as many as 100,000 new workers to help meet the increased demand, and even ordered a custom line of robotic equipment to facilitate the production of iPhone 6.

The larger of the two models is rumored to be experiencing some manufacturing difficulties, however, and could potentially be delayed until early 2015, though some reports say both versions will ship simultaneously later this year. As noted by the Wall Street Journal:

For Apple, one possible hiccup with the larger screen is that display makers for the new iPhones are struggling to improve the production of the larger 5.5-inch screens, people familiar with the matter said. The production is complicated because the displays are using in-cell technology, which allows the screens to be thinner and lighter by integrating touch sensors into the liquid crystal display and making it unnecessary to have a separate touch-screen layer.

We’ve seen a host of leaks for the 4.7-inch device in recent weeks, as well as a few for the 5.5-inch variant, though leaks of the larger model seem to be harder to come by. The unannounced phone’s sapphire crystal display was put through a series of stress tests on video and its audio and lightning ports showed up in online photos.