The term 'Jet Problem' is a type of problem that occurs in aircraft engines. It is caused by the accumulation of fuel and air in the combustion chamber, which can lead to a decrease in engine performance. The solution to this problem is to reduce the amount of fuel and air entering the combustion chamber, which is known as 'LAG' (3 letters). LAG stands for 'Lean Air/Fuel Ratio', which is the ratio of air to fuel that is used in the combustion process. By reducing the amount of fuel and air entering the combustion chamber, the jet problem can be solved.