Collagen coating of Transwell inserts and tissue culture-treated cell culture flasks is not required when expanding HAECs in PneumaCult-Ex Plus Medium or differentiating in PneumaCult-ALI Medium or PneumaCult-ALI-S Medium. We have not found any performance differences between coated and non-coated conditions; however, collagen coating may improve differentiation in some donors, or if working with freshly isolated cells.