The 601-1A received its Supplemental Type Certificate (STC for the 1A) in 1983. It was in production from 1983 to 1987 and 66 were produced. It is essentially a model 600 with General Electric CF-34-1A engines. When the engines go through hot-section or overhaul they may be upgraded to the 601-3A performance. More than half the fleet has taken advantage of this option. The range of the 601-1A with seats full is 3,180 nm with NBAA IFR reserves.