jongar: and that is relevant how?

The rest: Delta and American have each signed exclusive supplier agreements with Boeing (for a 20 year period, I believe) that, among other things, gives them guaranteed low volume prices and a great deal of flexibility in substituting aircraft types and delivery dates.

As to the biggest customer of Boeing. I don't know, but it would depend on whether you were counting airplanes, $$ spent, or were restricting it to a particular time frame.


------------------
"Service" should be a noun, not a verb.