Yesterday, the US Air Force said its fleet of F-35A fighter jets are ready for battle — finally. The planes were actually ordered 15 years ago, but their development was plagued by numerous delays and cost overruns. The Air Force is the second branch of the US military after the Marine Corps to approve the plane for combat, and the jets are now deployed at the Hill Air Force Base in Utah as part of the 34th Fighter Squadron. From there they can be launched into combat operations anywhere in the world.

The jet has had some issues

The US government awarded Lockheed Martin the contract to build the F-35A in October 2001. Nine years later, after the price per-plane had nearly doubled, US Defense Secretary Robert Gates still hailed it as the "backbone of US air combat for the next generation." By 2012, the lifetime cost of the program had swelled to a staggering $1.5 trillion. And the following year, the production of the aircraft had become so troubling that the Pentagon was considering canceling its orders altogether.

A litany of issues have surrounded the F-35A's development. In 2009, The Wall Street Journal reported that during the previous two years spies, possibly from China, had downloaded several terabytes of data on the F-35A's design and electrical system (although Lockheed assured the project had not been compromised). Then, in 2014, a F-35A caught fire while preparing for take off. An investigation found that due to design issues, pieces of the plane's internal fan blade had broken off and cut through the internal fuel tank and hydraulic and fuel lines, creating an explosion.

Earlier this year, the Air Force hit a snag in approving its F-35As for combat when it identified instances of software instability that caused the jet to have trouble starting up and triggered the random shutdown of sensors while running.

The F-35A's radar screen does not display data intuitively

At a press conference, General Herbert "Hawk" Carlisle said the F-35A isn't perfect, but its ability to "penetrate defensive airspace, deliver precision munitions with a sensor suit that fuses data with multiple information sources, is something our nation needs." The Air Force approved the fleet while acknowledging the jets' unresolved issues. During recent testing, for example, the Air Force found that the F-35A's radar screen did not always display data in an intuitive way, forcing the pilot to manually select a data point to get more information.

Carlisle said the Air Force is hoping to fix the issue with a software patch next year.