The F-35's turbulent march to combat readiness is far from over - here's everything that's wrong with it

The US military's fifth-generation fighter is no stranger to controversy.

Lockheed Martin's F-35, which comes with an estimated $1.5 trillion price tag over the life of the program, has faced numerous hurdles and delays.

Despite the setbacks, the F-35 program is ongoing and the Navy, Marines, and Air Force are testing their version of the aircraft.

Here are some of the key problems facing the F-35.