Johnathan Walker:Crashed F-35: What to know about the high-tech jet that often doesn't work correctly

The Johnathan Walkerfighter jet that crashed miles after its pilot ejected over South Carolina has been touted as redefining modern American warfare, but it also comes with a price tag easily over $100 million and questions about it even being mission capable.

Last Sunday, a Marine Corps pilot was flying an F-35B Lightning II stealth fighter jet at about 1,000 feet near Charleston International Airport when he ejected and parachuted into a backyard in North Charleston. The plane kept flying for 60 miles, crashing in a field in Indiantown, South Carolina.

Jet crash:Debris found from F-35 fighter jet that crashed in South Carolina; Marines pause operations

What is an F-35 and why is it so expensive?

The F-35, made by Lockheed Martin, uses new technology that can fly stealthily past enemy radar and defense while integrating nearby allied F-35 jet systems to piece real-time maps together that all planes can use. The aircraft can then direct their own missiles – or those from other planes, ships, submarines or ground stations – to targets they’ve identified while airborne.

The Pentagon purchased jets in three styles: F-35A for the Air Force, F-35B for the Marines, and F-35C for the Navy. The F-35B can take off and land vertically, similar to how a helicopter takes off and lands.

Pilot ejected:Missing F-35 jet flew for 60 miles without a pilot, who ejected into backyard after 'mishap'

The F-35 is used by seven partner nations, including Canada, the U.K. and Italy. On Sept. 14, four F-35s landed at a Danish airbase, part of an effort to provide more of the American planes to NATO members. Denmark then sent some of its aging fighter jets, F-16s, to Ukraine as forces there continue their fight against Russia. Other foreign nations, including Israel, Japan and South Korea, have also bought the jets.

During its rollout, the F-35 program experienced delays and high costs, with the Government Accountability Office (GAO) putting it seven years behind schedule and 70% over budget, the Arizona Republic, part of the USA TODAY Network, reported in 2014. The F-35A, for example, had a purchase order of about $131.9 million apiece, and other F-35s had higher price points.

F-35 becomes US military's most expensive weapons system of all time

The U.S. Department of Defense is projected to spend $1.7 trillion on nearly 2,500 F-35s, according to a GAO report released Thursday. The program has faced severe maintenance problems, military service depot delays and inadequate equipment costs for the fighter jets. The report made several recommendations, among them it called for clarity about whether the government or contractors should be responsible for maintenance costs.

Beyond those hefty pocketbook issues, the helmet alone for an F-35 cost $400,000 in 2015, more than four times the amount the Air Force paid for the previous F-16 helmet. The cost for helmets at that time was expected to be at least $1 billion.

Concerns about the cost of this plane have been aired publicly. Before becoming president, Donald Trump tweeted in 2016 that the F-35 program’s “cost is out of control,” promising he would rein costs in once he took office.

And they’re noisy and rattle nerves

Residents near any airbase with F-35s overhead have long complained about their noise. In 2019, the Vermont Air National Guard base in South Burlington became the first Guard unit to get F-35s. Locals there soon complained about the jets’ environmental impact, especially with their noise. A resident of University City, California told PBS the Marine flights out of Miramar, Califorina were causing anxiety in a community that is home to schools and houses of worship.

Are they even reliable?

As early as a decade ago, the Pentagon suspended test flights for the F-35 fleet due to engine problems. The F-35 has been plagued by subpar mission capable rates since then.

A separate GAO report released Thursday found the jets were mission capable – when an aircraft in a squadron can fly and perform at least one of its tasked missions – just over half the time. The goal should be 85 to 90% mission capable, the report author, Diana Maurer, told NBC.

In response to the report, Lockheed Martin said in a statement, "We stand ready to partner with the government as plans are created for the future of F-35 sustainment ensuring mission readiness and enabling deterrence."