Grecian.
I seriously doubt that even JB is planning to tackle Netjets head on. As any insider of NJE will tell you however they (NJE) have chinks in their armour.
JR employs a number of people who held key positions within NJE and therefore have intimate knowledge of their operation, clientbase and the like. No doubt they'll be avoiding the mistakes NJE have made because they saw them happen first time around. I'd also bet they'll be vastly more efficient on the operations side although in some areas that wouldn't be terribly difficult. Training and retaining staff rather than just giving them a desk and phone under the eye of a despot and constantly renewing their 'temporary' contract would be a good start. Remember also that by the time Jet Republic get going any 'anti-conflict' or confidentiality clauses in the ex-NJE staff's contracts that prevented them from exploiting their time there will have expired.
From the sidelines it's going to be interesting to see how this one goes.