The Bombardier Challenger 601 and 604 are both business jets, with the 604 being a significant upgrade to the 601, featuring improved range, more powerful engines, a larger fuel capacity, and enhanced avionics systems, allowing for longer flights and greater passenger comfort, while maintaining a similar cabin size; essentially, the 604 is a longer-range version of the 601, considered one of the best-selling models in the Challenger series, produced by Bombardier from 1995 to 2006.