Rapid increase of computational capability with high performance processors and parallel processing and continual cost-down of hardware make overlooked numerical methods revive for their own favorable nature. Dynamic Programming is one of the cases in the trajectory optimization. This paper pursues possibility of Dynamic Programming as a numerical method for flight trajectory optimization of aerospace vehicles. It examines two application examples of winged space vehicle's reentry flight and fuel efficient flight of a jet passenger aircraft to demonstrate advantages of Dynamic Programming. It also discusses how to overcome disadvantages of Dynamic Programming, such as a large amount of computational time and quantization errors.