These premium passengers flew Chicago-Frankfurt on a United Boeing 787 in April. (Photo by Nicolas ... [+] Economou)NurPhoto via Getty ImagesAmerican Airlines said Thursday that it will lose $1.5 billion in revenue this year due to a failed effort to bypass traditional corporate buying channels.It’s not quite clear where the money went. Delta and United have been coy in discussing whether American’s loss benefitted them. American did not respond to an emailed question on the topic.Dennis Tajer, spokesman fo ...