The purchase price for Milestone could be more than $2.5 billion, according to some of the people, the Journal reported. Milestone, co-founded by NetJets Inc founder Richard Santulli, has announced plans for an initial public offering of stock, according to the report. Buying Milestone, the world’s largest helicopter-leasing company by fleet value, would broaden GE Capital Aviation Services’ portfolio beyond the competitive plane-leasing business, as it currently owns no helicopters, the Journal said.