Harvard Business Publishing makes a great deal of money selling these for business school course packs and will not make them available to libraries. You can, however, order them directly from HBS, around $8.95 each
How to find them:
Use keyword searches in article databases . For example: "case studies and airlines" or "case studies and management". Full-text articles and abstracts are available, depending on the journal.
Tip: Use the subject heading "case studies" in ABI/INFORM and Business Source Complete
Most cases published for teaching in business schools are not free to use. These are a few resources that do offer free cases, but only LearningEdge offers their entire catalog for free.