Deltas use of the term is actual trademark infringement in a classic sense. The use of the term directly infringes on Americans mark and creates confusion in thr marketplace with similar if not identical customers. I think AA will prevail in this lawsuit and frankly DL should know better. The only way they will get off is by either claiming the term flagship is non distinctive and therefore not a real trademark, something very hard to do in the USA after registration, or they will have to prove prior use.