NetJets Inc., announced Friday it will significantly expand its fleet of large-cabin Gulfstream G450s and Gulfstream G550s. In a new agreement signed with Gulfstream valued at $1.9 billion, 40 new Gulfstream aircraft - 20 Gulfstream G450s and 20 Gulfstream G550s four to be delivered each year from 2012 through 2016. The deal also includes a long-term maintenance support agreement