This is a bit confusing to a lot of people. NetJets is the world’s largest operator of private jets. It is owned by Berkshire Hathaway whose CEO is one of the world’s richest men, Warren Buffett. NetJets has an arm called Executive Jet Management, or EJM, that manages private jets on behalf of their owners. NetJets sells fractional shares in private jets. This is akin to a time share where you actually own part of a specific jet, but then get access to the fleet. The minimum share you can buy is 50 hours representing 1/16th of a plane.
NetJets also sells jet cards under the banner, Marquis Jet Card. Marquis Jet Partners was originally a separate company started by Kenny Dichter, who sold Marquis Jet to NetJets and then started Wheels Up. which is focused around a turboprop fleet of King Air 350i. NetJets sells the Marquis Jet Card in 25 and 50-hour denominations. You then get access to fly on the fleet owned and operated by NetJets, although your access will be slightly different than owners in terms of how many hours in advance you need to make a reservation (10 hours versus as little as 4) and also peak days (30 vs. 10), etc. You can get a full comparison of all Marquis Jet Card programs by clicking here.