The original programme cost estimate was £70 million. The programme experienced huge overruns and delays, with the program eventually costing £1.3 billion. It was this extreme cost that became the main factor in the production run being much smaller than anticipated. Later, another factor, which affected the viability of all supersonic transport programmes, was that supersonic flight could be used only on ocean-crossing routes, to prevent sonic boom disturbance over populated areas. With only seven airframes each being operated by the British and French, the per-unit cost was impossible to recoup, so the French and British governments absorbed the development costs. British Airways and Air France were able to operate Concorde at a profit after purchasing their aircraft from their respective governments at a steep discount in comparison to the program's development and procurement costs.