Increasing numbers of BAe 146 and Avro RJ regional aircraft are becoming available for VIP or specialist conversion.
German company Cordner Aviation, set up by former Avro Business Jet executive Stewart Cordner in February this year, has 16 aircraft pledged to it.
A number of these are due to be defleeted by companies in the Balkan Aviation Group later this year and into early 2012, said Cordner.
According to Flightglobal's ACAS database, Bulgaria Air operates a total of four BAe 146s, and sister company Hemus Air a further two of the aircraft.
Another two are from an unnamed European airline, Cordner added.
A "significant number" are also available from Falko, the former BAE Systems leasing unit, he said. "It's very much a sales market on the 146," he said. "It's not worth the risk leasing them."