In its latest monthly business jet report, released last week, investment research firm UBS saw a slight increase in the overall used aircraft inventory in November, its fourth straight monthly increase following a steady declining trend over the past 14 months. Available aircraft inventories were 3 percent higher than those in July. According to the analysts, the increase is driven by young available aircraft (0-10 years old) whose availability is 7 percent higher than it was in July. UBS estimates that 15 percent of the fleet is currently available, down from the peak of 18 percent, but still above the historical average of 12 to 13 percent. Despite these numbers, based on its responses to its most recent survey, UBS noted an improvement in customer interest. In October, 33 percent of the respondents indicated that customer interest had increased. The number rose to 41 percent in December, thanks mainly to a strengthening of the underlying market conditions.