Current plans are that 19 joint strike fighters will be used for the system development and demonstration (SDD) for JSF. The UK share for these are covered by our fixed $2 billion contribution to SDD. The UK's contribution to the joint operational test and evaluation of JSF with the US services is two aircraft. Instructor training will be conducted through a combination of simulator training and use of operational conversion unit aircraft and the UK operational conversion unit will build over time to 16 aircraft. Other than the SDD aircraft the UK has made no commitments to purchase aircraft and we will continue to monitor requirements as the programme matures.