Unlike the inventories of pre-owned business jets and turboprops, the inventory of used turbine helicopters remains low (below 7 percent of the in-service fleet) and thus is a seller’s market, according to data compiled by Utica, N.Y.-based JetNet, a research company specializing in business aircraft.

At the end of April, the turbine helicopter inventory stood at 6.9 percent (1,160 aircraft), slightly higher than the 6.2 percent seen a year ago but still below the 10 percent that denotes market equilibrium.

The number of pre-owned sale transactions for turbine helicopters increased by 13.5 percent, to 394, in the first four months compared with the same period last year. However, the average number of days on the market for turbine helicopters increased 82 days, to 314, in the first trimester compared with 2009. The average asking price also increased by 3.2 percent from a year ago.

Meanwhile, piston helicopter inventory inched down from 7 percent in April 2009 to 6.5 percent in the same month this year. Pre-owned sale transactions for piston helicopters decreased by 17.7 percent in the first four months versus the same period last year. Average days on the market for piston helicopters climbed by 80 days, to 282, in the trimester compared with a year ago, but average asking prices still increased by 3.1 percent.