Boeing and Airbus, the duopoly makers of big jets, have joined forces to oppose plans by Canada’s Bombardier to seek more liberal terms for export credit financing for its new range of short-haul aircraft.

The fierce US and European rivals are contesting the Canadian group’s proposal to categorise its new CSeries range of 110 to 130-seat aircraft as regional jets, rather than large aircraft, under a set of Organisation for Economic Co-operation and Development rules for export credit finance. The rules are known as the aircraft sector understanding.