The F-35 Lightning II's problems include hundreds of software vulnerabilities and guns that don't shoot straight, according to a new Pentagon report on issues with Lockheed Martin's $428 billion program.

Air Force models of the F-35 use an internally mounted 25mm Gatling gun that has 'unacceptable' accuracy due to 'misalignments,' according to an upcoming report from the Pentagon's test office obtained by Bloomberg.

The mounts on the guns are also cracking, forcing the Air Force to restrict use of the gun, the report says.

The Marine and Navy versions of the Joint Strike Fighter use an externally mounted version of the gun that does not have the same issues, according to the report.

Air Force models of the F-35 (like the one above) use an internally mounted 25mm Gatling gun that has 'unacceptable' accuracy due to 'misalignments'

The report from the Defense Department's director of operational test and evaluation, which could be publicly released as soon as Friday, identifies 13 'must-fix' problems that affect safety or combat capability.

It does not reveal any major new failings in the plane's flying capabilities, however.

The number of software deficiencies totaled 873 as of November, according to the report, down from 917 a year earlier.

The report also identifies a number of cybersecurity vulnerabilities that were identified in previous reports but have not yet been resolved.

The F-35 Lightning II's issues include hundreds of software vulnerabilities and guns that don't shoot straight, according to a new Pentagon report

Brett Ashworth, a spokesman for Bethesda, Lockheed Martin, told Bloomberg that 'although we have not seen the report, the F-35 continues to mature and is the most lethal, survivable and connected fighter in the world.'

He said 'reliability continues to improve, with the global fleet averaging greater than 65% mission capable rates and operational units consistently performing near 75%.'

So far, at least 491 F-35s have been delivered to customers including the US, UK, Australia and Netherlands at a cost of roughly $100 million apiece.

The issues will have to be fixed on the already-delivered planes, which according to the testing office are running six different versions of software.