Billionaires and big companies have had tens of millions of dollars wiped off the value of their business jets, as massive oversupply in the run-up to the 2008-09 credit crisis has left the industry awash with pre-owned aircraft.Prices for second-hand jets, many of which have barely been flown, have dropped up to 35 per cent over three years to the end of April. The average price has fallen from $13.7m in April 2014 to $8.9m, according to Colibri -Aircraft, which markets, resells and purchases pre-owned private aircraft. Owners have lost millions on the value of existing jets after a glut hit the market after the downturn. The resale price of a Bombardier Global XRS, which sold for $50m, has dropped from $31.3m to $20.4m — down just under 35 per cent, say Colibri’s figures.Bombardier said it did not comment on specific pricing but had realigned production in the light of demand.Newer models coming to the market had caused prices to fall further, said Oliver Stone, Colibri managing director. “Customers are selling their current jet to upgrade to the new one,” he said. “Supply is increasing, but not demand.”Deliveries of new business jets have fallen dramatically over the past decade. In 2016, 661 planes were delivered, compared with 1,313 in 2008. “Pre-2008, the jet market was in a massive bubble and prices have been decreasing ever since,” said Mr Stone.