B-2 clouds 2002
A U.S. Air Force B-2. Reuters

The world's militaries this year will spend an estimated $1.84 trillion on everything from boots to battleships, according to the Stockholm International Peace Research Institute. That's approximately $700 billion more than the entire African continent's gross domestic product.

Unsurprisingly, the United States tops the list with $682 billion, representing about 39 percent of the global total and 4.4 percent of the country’s GDP. In second spot is China, which spent $166 billion, approximately 2 percent of its GDP.

Here’s a top 10 list of the most expensive aircraft made in the U.S., is ascending order of price per unit:

10. F/A-18 Hornet: $94 million

This high-performance fighter-bomber is the budget option in this list. It was introduced into service in the 1980s with the U.S. Navy and Marines, saw action in Desert Storm, and became the aircraft of choice for the Navy’s Blue Angels Flight Demonstration Squadron. It is also in service in the Canadian, Australian, Swiss, Spanish, Malaysian, Finnish and Kuwaiti militaries.

9. EA-18G Growler: $102 million

Based on an update of the F/A-18 called the Super Hornet, it's currently being delivered to the Navy. While it’s similar to the F/A-18 Hornet, the Growler is a lightly armed version, meant to find and disrupt anti-aircraft radar and jam enemy communications.

8. V-22 Osprey: $118 million

The Osprey aircraft started off life under a dark cloud after it claimed the lives of 30 people during a crash while in development. Vice President Dick Cheney tried to have it grounded, but the versatility of its tiltrotor technology means it can take off like a helicopter but fly at speeds and distances comparable to a fixed-wing aircraft, so the Marine Corps were anxious to get it. It has since been used in Iraq and Afghanistan.

7. F-35 Lightning II: $122 million

Stealthy, supersonic fighter jets tend to cost a lot of money, and when Lockheed Martin Corporation (NYSE:LMT) signed the deal to manufacture it in 2001, it was the largest military contract ever. It was designed as part of a Joint Strike Fighter program that involved allied countries, but it was often criticized for being heavy and underpowered. An incredible 7.5 million lines of code was produced to help power the aircraft, but at one point the whole operation was put at risk when the code was infiltrated, raising concerns that other countries could copy the code and exploit weaknesses in the aircraft or even copy its technologies.

6. E-2D Advanced Hawkeye: $232 million

The updated version of the Navy's Hawkeye has increased surveillance and reconnaissance capabilities. Even though it is yet to enter service, analysts have already said it has breathtaking abilities, but cutbacks may mean its decades-old predecessor, the E-2C, will continue to serve aboard American aircraft carriers.

5. VH-71 Kestrel: $241 million

Built to replace the president’s old chopper fleet, the Kestrel was 50 percent over budget by the time President Barack Obama came to office. Obama asked that it be cut -- and the military did so in 2009, dedicating funding for the new helicopter to maintaining instead the existing fleet of presidential helicopters.

4. P-8A Poseidon: $290 million

It's basically The Boeing Company (NYSE:BA) 737 jet, but modified for the Navy to conduct anti-submarine warfare. It’s capable of carrying depth charges, torpedoes and missiles and is about to enter service at a full cost of $33.638 billion.

3. C17A Globemaster III: $328 million

This Air Force aircraft came into service in 1993 as a military transport plane, able to move troops into war zones, and conduct airdrops and medical evacuations. Besides its ability to drop 102 paratroopers in one go, it can move huge loads including Humvees, tanks and other vehicles, making it invaluable during conflicts in Iraq and Afghanistan. It will cease production in 2015 when its Long Beach, Calif., assembly plant closes.

2. F-22 Raptor: $350 million

Allegedly the world’s best fighter, it was originally conceived to compete with a Soviet enemy that has since vanished. It’s undetectable from enemy radar and can shoot down cruise missiles while flying long distances at supersonic speeds. Production was shut down after less than 200 were delivered. The Air Force wanted hundreds more.

1. B-2 Spirit: $2.4 billion

Its breathtaking appearance looks more like an alien spacecraft than a high-tech bomber whose design process was started in the 1970s and had its first flight in 1989. It was so expensive that the government had to cut back its original purchase of 132 to just 21, of which 20 are still functioning after a crash in 2008. The aircraft has been around for so long because it’s very hard to detect via infrared, electromagnetic, visual or radar signals – primarily because of its incredible flat design.