F-35 fighter jets used by the US Navy and Marine forces are so unpredictable at top speeds that pilots fear they would be unusable in dogfights, new documents reveal.

Pilots have reported erratic handling when approaching max performance including unpredictable changes in pitch and rolling motions — both of which are considered a 'category 1 deficiency', the most serious type of deficiency.

According to the report, aviators said the issue would 'prevent repeatable air-to-air combat techniques resulting in mid-air collisions during training,' as well as 'aircraft loss during combat engagements with adversary aircraft and missiles.'

The $100million-apiece-jets, considered the most advanced military aircraft's ever designed, have been plagued with issues since their roll out but the documents obtained by Defense News has shed new light on the true extent of the problems.

F-35 fighter jets used by the US Navy and Marine forces are so unpredictable at top speeds that pilots fear they would be unusable in dogfights, new documents reveal (An F-35C Lightning II test aircraft approaches for a landing aboard the nuclear powered aircraft carrier USS Dwight D. Eisenhower)

Documents reveal that a version used by Marines and a Navy's carrier-launched version become so difficult to control when the aircraft is operating above a 20-degree angle of attack — crucial in dogfights when pilots must dodge incoming missile strikes — that they would be ineffective when needed most.

Such is the scale of the problem that the damning report defines it as something that limits the aircraft's performance to such an extent that it cannot accomplish its 'primary or alternate mission(s).'

According to Defense News, Lockheed Martin, the aerospace and defense company behind the F-35, defended the aircraft and said the issues would be 'resolved or downgraded soon as a result of software fixes.'

'We've implemented an update to the flight control system that is planned for integration in the third quarter of this year — and we expect this item to be resolved or downgraded,' said Lockheed Martin vice president Greg Ulmer.

Despite this, a retired Navy fighter pilot who reviewed the documents blasted the F-35's failure to maneuver at high speeds, adding: 'You're telling me that the latest, greatest, $100 million aircraft can't perform?'

Such is the scale of the problem that the damning report defines it as something that limits the aircraft's performance to such an extent that it cannot accomplish its 'primary or alternate mission(s)' (file image of an F-35C Lightning II test aircraft)

The handling issue compounds the previously documented issue the jets suffer in that at extremely high altitudes, the Navy and Marine Corps version can only fly at supersonic speeds for short bursts of time without risking structural damage to the aircraft.

In a statement addressing the problems listed in the report, Ulmer, the Lockheed executive, defended the performance of the jet and said they are already 'meeting or exceeding performance specifications and delivering unprecedented capability.

Adding: 'These issues are important to address, and each is well understood, resolved or on a path to resolution,' Ulmer said.

F-35 firepower Top speed: 1.6 Mach Weaponry: 5,700 pounds of internal ordnance (stealth mode) and 22,000 pounds of combined internal and external weapons (beast mode). The F-35 Lightning II is referred to as a 5th Generation fighter, combining advanced stealth capabilities with fighter aircraft speed and agility, fully-fused sensor information, network-enabled operations and advanced logistics and sustainment. Advertisement

'We've worked collaboratively with our customers and we are fully confident in the F-35's performance and the solutions in place to address each of the items identified.'

In previous testing reports, other 'serious' issues found in testing include spikes in cockpit pressure that can give pilots sinus pain, the loss of control on certain manoeuvres, and a system error causing the plane to erroneously report battery problems in cold conditions.

While Pentagon officials also warned that the jets can only fly at supersonic speeds for short bursts, or the stealth coating will 'blister'.

Deficiencies with the stealth coating, which makes planes invisible to radar by absorbing radio waves, were uncovered following tests in 2011 when an F-35B and F-35C flew at speeds between 997 and 1074mph.

During the British trials the F-35s have not been tested to the same extreme limits as in the US, so not all of the same issues have been experienced.

Britain plans to eventually buy 138 F-35s as part of a massive £9.1billion ($11.5bn) deal that has been plagued by problems.

F-35 fact file: How the jets cost $100m each, fly at a maximum speed of 1,200mph and include more than 300,000 different parts – The jet measures 51.2ft in overall length, has a wingspan of 35ft and a height of 14.3ft. – It has a top speed of 1.6 Mach or 1,200 mph, a Max G rating of 7G, and a combat radius of 518 miles. – Lockheed Martin, who built the jet, describes its stealth capabilities as 'unprecedented'. Its airframe design, advanced materials and other features make it 'virtually undetectable to enemy radar'. There are three different varieties of the F35, which each have separate features, as show above – The F-35B jets are built from more than 300,000 individual parts. – There are six distributed aperture system sensors around the jet – two underneath, two on top of the aircraft and one either side of the nose. These infrared cameras feed real-time information and images into the pilot's helmet, allowing them to see through the airframe. – All variants of the jets are mainly constructed on Lockheed Martin's mile-long production line in Fort Worth, Texas. – It takes 58,000 man hours to build each F-35B. – The F-35 can launch from land, and will take off from HMS Queen Elizabeth via the skip jump ramp, which has been designed to optimise the launch. – Maximum thrust tops 40,000lb and the jet has a range of 900 nautical miles. – The jet is capable of two types of ship landing – vertically on to the deck, and also through the shipborne rolling vertical landing, which using forward air speed, allows the aircraft to bring back several thousand pounds of extra weight to the ship. Advertisement