Though the early Lockheed Jetstar had four, most production business jets have two jet engines, mostly rear-mounted podded engine. If mounted below their low wing, it wouldn't allow sufficient engine clearance without a too long landing gear. The HondaJet is the exception with its over the wing engine pods. Dassault Falcon still builds three-engine models derived from the Falcon 50, and the very light jet market has seen several single-engine design concepts and the introduction of the Cirrus Vision SF50 in 2016.
Charter operators own or manage private jets for multiple clients. Like traditional flight departments, charter companies handle all aspects of aircraft operation and maintenance. However, they are not aligned with just one corporation. They manage aircraft for a private owner or corporation and also handle the sales of available flight time on the aircraft they own or manage. Maintenance services can also be provided which typically include on-site or mobile repair, major and minor routine inspections, troubleshooting assistance away from base, avionics installation and repair, jet engine and battery service, interior modifications and refurbishment, Inspection Authority (IA) qualified inspectors, aircraft planning and budgetary projections, compliance with service bulletins, aircraft storage management, record keeping and management, technical appraisal of private jet purchases, leases and lease terminations, and Part 91 or Part 135 conformity inspections.
On 1 April 2017, there were 22,368 business jets in the worldwide fleet, of which 11.2% were for sale. 5-year old aircraft residual value level is at a 56% of the list price. A new business aircraft depreciate by 50% in five years before depreciation flattens between years 10 and 15, and the owner of a 15 to 20 years old is often the last, matching luxury cars.