Lung transplantation is increasingly employed as a therapy for patients with advanced lung disease including cystic fibrosis, idiopathic pulmonary fibrosis or emphysema. Despite significant short-term improvements in life quality and measures of lung function after lung transplantation, long-term outcomes are disappointing primarily due to the development of a condition of airway fibrosis known as bronchiolitis obliterans (BO). It is hypothesized that aztreonam lysine for inhalation (AZLI) is a safe and effective treatment for declining lung function in lung transplant recipients with early stage BOS. In order to test the hypothesis, the investigators seek to establish the safety of AZLI in a two-center cohort of 30 lung transplant recipients with BOS treated intermittently for 5 consecutive study months and determine if this treatment leads to improvement or stabilization of lung function. The intervention will involve open label treatment with AZLI, in addition to usual transplant care, administered for 3 intermittent courses, 28 days each, over a 5 month study period.. Bronchoscopy, pulmonary function testing, and laboratory testing will be performed on a regular basis during study enrollment consistent with each center's usual standard clinical care. Patients will have a baseline screening visit, one month and five month study visit.. The study will take two years to complete from the start of funding. After a start-up period of 2 months, a total of 30 patients will be enrolled over 12 months across the two centers (15 patients each at DUMC and UCLA). Each enrolled patient will complete 5 months of intermittent therapy, and complete baseline, month 1 and month 5 visits. Over the next 6 months the study database will be finalized, statistical analysis will for primary and secondary outcomes will be performed leading to the generation of either a study abstract or manuscript.