Netjets has several audited and approved charter companies that provide supplemental lift during peak period times when the combined Netjets fleets are not adequate to meet demand. The primary vendor used is Executive Jet Management. EJM is a sister company that provides aircraft management services to owners across the country that prefer to own their entire aircraft. These owners frequently offer their aircraft for charter for either revenue or tax purposes. EJM provides the 135 certificate, training, and record-keeping so that these aircraft may be chartered. Last I read, the number of aircraft managed by EJM exceeded 100 and included a wide variety of popular business aircraft.
Marquis Jet is strictly a re-marketing company. They do not hold a 135 certificate. Marquis Jet actually owns shares of aircraft in the regular Netjets fleets and re-sells their time to individuals who either don't want or can't afford their own fractional share. Many Marquis customers are high income but not yet high net worth individuals such as athletes, actors, musicians, and business owners. When a Marquis Jet Card customer flies on board a Netjets aircraft, they are not "owners" of a share and therefore the flight cannot be conducted under Part 91K but must be operated under Part 135.
Clear as mud?