The Pentagon announced this week that the projected total cost for buying the F-35 has spiked this year, driven mostly by slower-than-expected United States Air Force procurement. This is an increase of $27 billion on a program that has been over-budget for almost a decade.

Here is what you should know about the most expensive military weapons system in history.

 F-35B Lightning II
PACIFIC OCEAN (Nov. 19, 2016) An F-35B Lightning II hovers before landing aboard the USS America (LHA 6) during the Lightning Carrier Proof of Concept Demonstration. The demonstration is the first shipboard Marine Corps F-35B integration demonstration alongside other Marine Corps Air Combat Element assets. U.S. Marine Corps Photo by Cpl. Thor Larson/Released.

1. The F-35 program is a military weapons program to design, build, and maintain the F-35, a single-engine, single-seat fifth-generation joint strike fighter (JSF) aircraft. When completed, the F-35 aircraft will be the world’s most advanced multi-role fighter jet. It is scheduled to be the primary fighter plane used by the U.S. military until the year 2070.

2. The F-35 is designed to replace several aging “fourth generation” fighter inventories, and includes three variants: the F-35A conventional takeoff and landing (CTOL) variant (which will replace the U.S. Air Force’s A-10s and F-16s), the F-35B short takeoff/vertical landing (STOVL) variant (which will replace the AV-8B Harriers used by the United Kingdom and the U.S. Marine Corps), and the F-35C carrier variant (CV) (which will replace the F/A-18s used by the U.S. Navy and Marine Corps).

3. While the F-35 program is primarily funded by the U.S., twelve other countries are also participants in the funding and development of the project: Australia, Canada, Denmark, Italy, the Netherlands, Norway, Turkey, and the U.K. Three other countries—Israel, Japan, and South Korea—have also contracted to buy the aircraft.

Marine Corps F-35B Lightning II
PACIFIC OCEAN (Jan. 9, 2017) Two Marine Corps F-35B Lightning II, assigned to Marine Fighter Attack Squadron (VMFA) 121, 3rd Marine Aircraft Wing, transit the Pacific Ocean on their way to Marine Corps Air Station Iwakuni, Japan, to join the 1st Marine Aircraft Wing. VMFA-121, originally an F/A-18 squadron, was re-designated in 2012 as the Marine Corps’ first F-35 squadron. U.S. Marine Corps photo by Sgt. Lillian Stephens/Released.

4. The F-35 program had its origination in several programs from the late 1980s and early 1990s. In 1997, Lockheed Martin was selected as one of two companies to participate in the Joint Strike Fighter concept demonstration phase. In October 2001, the Lockheed Martin X-35 was chosen as the winner of the competition and teamed with Northrop Grumman and BAE Systems to begin production. In December of 2006, the F-35 completed its first flight. In 2001, Lockheed announced the F-35 would be combat-ready by 2010, but has yet to be fully deployed. The U.S. Marine Corps declared their first squadron of 10 F-35Bs ready for world-wide deployment in 2015. The U.S. Air Force announced their F-35As ready in 2016. The Navy’s aircraft are scheduled to be ready in 2018.

5. The F-35 is one of the most complex military programs in history. The aircraft is assembled in three factories around the globe (Texas, Italy, and Japan), contains 300,000 parts made from 1,500 international suppliers, and contains more lines of code than it took to launch the Space Shuttle.

F-35 Lightning II helmet
An F-35 Lightning II helmet during the Air Force Association’s Air, Space and Cyber Conference in National Harbor, Md., Sept. 20, 2016. The F-35’s helmet mounted display system is the most advanced system of its kind. All the intelligence and targeting information an F-35 pilot needs to complete the mission is displayed on the helmet’s visor. U.S. Air Force photo by Tech. Sgt. Anthony Nelson Jr.

6. The complexity of the F-35 is often blamed for the program’s failures. As Popular Mechanics notes,

In the decade following 2003, the program faced over a dozen major setbacks. They just kept coming and coming. In 2004, the F-35B was more than 2,000 pounds overweight, unable to meet its performance goals. In 2006, the Government Accountability Office (GAO) warned that, as a result of the policy of concurrent development, retrofitting aircraft with systems that were not fully functional or working as intended could be terribly expensive. By 2013, the cost of retrofitting was put at $1.7 billion.

7. The current costs per aircraft, according to Lockheed Martin, varies by the type: F-35As CTOL – $94.6 million; F-35Bs STOVL – $122.8 million; F-35Cs CV – $121.8 million. In comparison an F-16 costs $18.8 million, an AV-8B costs about $30 million, an F-14 costs $38 million, and an F-18 costs $98.3 million.

8. The cost to operate the aircraft is also higher per hour than other military jets. The F-35A has an hourly operating cost of $28,455, compared to $5,944 for an A-10, $8,278 for an F-16, $10,507 for an F-18, and $13,788 for an AV-8B.

integration of the F-35 with existing Naval Integrated Fire Control-Counter Air
WASHINGTON, D.C. (Sept. 13, 2016) This graphic illustration depicts the U.S. Navy’s first live fire demonstration to successfully test the integration of the F-35 with existing Naval Integrated Fire Control-Counter Air (NIFC-CA) architecture. During the test at White Sands Missile Range, New Mexico, Sept. 12, an unmodified U.S. Marine Corps F-35B acted as an elevated sensor to detect an over-the-horizon threat. The aircraft then sent data through its Multi-Function Advanced Data Link to a ground station connected to USS Desert Ship (LLS 1), a land-based launch facility designed to simulate a ship at sea. Using the latest Aegis Weapon System Baseline 9.C1 and a Standard Missile 6, the system successfully detected and engaged the target. U.S. Navy graphic illustration courtesy of Lockheed Martin/Released.

9. A presentation by the director of the Pentagon’s in-house testing office dated May 8 and obtained by Bloomberg said that the F-35 isn’t as reliable as expected and is taking longer to repair than planned. “The presentation was prepared for defense officials and congressional aides,” reports Paul Barrett. “It explained that about 20 percent of F-35s are stuck in maintenance depots because suppliers can’t keep up with expanding production while also fixing returned parts. The availability of spare parts for the more than 200 F-35s already assigned to bases ‘is getting worse, affecting fly rates’ and pilot training, according to the presentation.”

10. The newly released Selected Acquisition Report finds that the total acquisition cost of the program may rise about 7 percent to $406.5 billion. According to Bloomberg’s Anthony Capaccio, that’s a reversal after several years of estimates that had declined to $379 billion recently from a previous high of $398.5 billion in early 2014. Capaccio also says that, “The estimate for the overall average per-jet program acquisition cost in current dollars—the most complete measure of a weapon’s cost—increased to $164.6 million per jet from $154.3 million, according to the release.” Paul Barrett adds that, “When operations and maintenance of the F-35 are factored in, the total will likely exceed $1.1 trillion over the decades to come.”

Joe Carter is an adjunct professor of journalism at Patrick Henry College, an editor for several organizations, and the author of the NIV Lifehacks Bible.

Feature Photo Credit: F-35 Lightning II’s from Hill Air Force Base, Utah, fly in formation during a training flight May 2, 2017. F-35 pilots are using the airframe in its first-ever flying training deployment to Europe. U.S. Air Force photo by Senior Airman Christine Groening.