The eight remaining cooks head to RAF Halton in Aylesbury to celebrate 100 years of the RAF's formation. They are split into two teams of four and face the challenge of running their own kitchens to create two main courses and a dessert to feed 120 veterans, serving airmen and new recruits for a special lunch that celebrates the centenary. With less than four hours to deliver, organisation and teamwork are essential for success. After judging their food, John and Gregg pick the weakest team to return to the MasterChef kitchen, where they cook-off against each other in a special Invention Test, using leftover produce from the previous challenge.