Maintainability analysis provides quantifiable assessment of the performance and effectiveness of the maintenance and support system so that further improvement actions can be made. This study presents a systematic and practical approach for conducting maintainability analysis at operational phase. The proposed approach is demonstrated via a case study of a gas compression train system. The results indicate the approach is effective in identifying key contributors to system downtime and estimating maintainability measures for future maintenance system improvement and planning. © 2012 Asian Network for Scientific Information.