The F-35 Joint Strike Fighter - $1.5 trillion (over 55 years)
Cost per unit: $100 million
The poster-child for troubled Pentagon programs everywhere, the F-35, in development for almost 16 years, is several years behind schedule and has cost around $400 billion to date. Conceived in 2001, the fifth-generation aircraft and its variants are meant to replace mutiple planes across the Air Force, Navy and Marine Corps. An endless string of setbacks has slowed the program, but last year, the Marines declared its version ready for deployment, and the Air Force hopes to do so this year.