Delta can't buy more than 49% of the shares; Etihad would presumably be delighted to offload their holding to Delta, and I can't see Delta wanting to be have Etihad as a major shareholder in the airline.

Delta may think that their de-facto control of Virgin Atlantic with a 49% shareholding can be replicated at Alitalia - but only if they ignore Etihad's experience.

I image that Delta are only being sticky beaks and trying to get a glimpse of the books, like the other 29 "interested" parties.