The Cessna Citation X is currently the fastest business jet and flying civilian airplane in the world with a traveling speed of up to 605 mph.  

In October 1990, the National Business Aviation Association Convention in New Orleans announced the development of the Citation X.  The certification of the Cessna Citation X was delayed several times.  The main reasons for the delays were the avionics and the engine integration failure to the aircraft, the engines also didn't pass the bird strike criteria and directional stability challenges.  The certification was finally approved on June 3, 1996.  

In June 1996, the first Citation X was delivered to Arnold Palmer, a golfer and avid Cessna customer.  The Citation X continued to set speed records.  In January 1, 2002, all Citation X underwent upgrade and the main characteristics of the upgraded version are a 5% increase in thrust, a 400 lbs increase in maximum take-off weight and improved Honeywell avionics.

The Citation X incorporates a number of innovative design features; large diameter of the engine intakes, reduced noise from the engines and improved fuel efficiency.  The Citation X was also the first aircraft from Cessna to use a Rolls-Royce engine and fully-integrated avionics.  Despite Cessna's long history of building business jets and the number of aircraft in the Citation family, the Citation X was a completely new design, not a derivative of earlier Citations.  

The Cessna Citation X is currently the fastest civilian aircraft being flown, though the Concorde and Tupolev Tu-144 were both faster, but they are no longer in service