 This single-center pilot study is designed as a double-blind, randomized, cross-over clinical trial to evaluate the effects of inhaled lucinactant, an investigational peptide-containing synthetic surfactant 6 ml of 20 mg total phospholipid TPLmL solution x 5 doses in patients with mild to moderate CF lung disease. Lucinactant and vehicle will be delivered via a 510k approved vibrating mesh nebulizer, the Pari eFlowTM. The study duration corresponds to a 2-10 day screening phase, followed by a 20 day post-randomization phase that consists of two treatment periods 3 days each and a washout period 14 days. A total of 16 patients will be enrolled and randomly assigned to one of two treatment sequences Lucinactant followed by vehicle or vehicle followed by lucinactant. The primary outcome will be the rate of MC, as assessed via gamma scintigraphy, post-lucinactant and post vehicle. Secondary outcomes will include the rate of cough clearance CC, lung clearance index LCI, absolute change from baseline in FEV1 after 5 doses of study medication, CF-specific quality of life score via CFQ-R instrument, in vitro assessments of sputum rheology, and various safety parameters. 