The Pentagon has decided to resume flights on its F-35 fighter jets, after the whole fleet was grounded last week.
A cracked turbine blade found on a plane prompted the suspension. But tests showed that this was a “unique” problem and not a design flaw, engine maker Pratt and Whitney said.
Thousands of F-35s are due to be made for the US and its foreign partners.
The F-35 is the Pentagon’s most expensive weapons programme, with a cost of nearly $400 billion.
The fault was detected during a routine inspection of an air force version of the jet (F-35A) at Edwards Air Force Base in California.
But on Thursday a spokesman for Pratt and Whitney, Matthew Bates, told Reuters news agency: “The team has determined that root cause is sufficiently understood for the F-35 to safely resume flights.”
Extensive tests on the plane’s engine revealed the crack was a result of the “unique operating environment” of the test flight, and was not a widespread issue, he added.
The engine had been running at high temperatures for four times longer than a normal F-35 flight, causing a separation of the “grain boundary” on one blade, Matthew Bates explained.
The Pentagon later confirmed that all its 51 planes had been cleared to resume flights.
The Pentagon has decided to resume flights on its F-35 fighter jets, after the whole fleet was grounded last week
Last week’s order to ground the planes – in the US air force, army and Marine Corps – marked the second time in two months planes from the F-35 range have been grounded.
The Marine Corps variant (F-35B), a short take-off and vertical landing variant (STOVL), was grounded for nearly a month after a manufacturing defect caused a fuel line to detach just before a training flight in January.
The F-35 programme includes partners from nine countries.
The construction of the plane has been plagued by problems – it is seven years behind schedule and has required numerous re-designs because of delays in software delivery and bulkhead cracks.
The US Air Force has announced that an attempt to fly its hypersonic jet X-51A WaveRider at Mach 6 (3,600 mph; 5795 km/h) has failed.
The unmanned aircraft had been designed to fly at six times the speed of sound after being dropped from a B-52 bomber.
But officials said that a faulty control fin prevented it from starting its supersonic-combustion ramjet engine, and the craft was lost.
It marks the second time in a row that the Air Force has been unable to test the technology as planned.
The US Air Force has announced that an attempt to fly its hypersonic jet X-51A WaveRider at Mach 6 (3,600 mph; 5795 km/h) has failed
The latest attempt had sought to fly at its maximum speed for five minutes.
But a spokesman said that a problem was recognized 16 seconds after a rocket booster was triggered to increase its velocity, ahead of the scramjet engine being started.
When the rocket unit detached 15 seconds later X-51A WaveRider lost control and broke apart, falling into the Pacific Ocean north-west of Los Angeles.
“It is unfortunate that a problem with this subsystem caused a termination before we could light the scramjet engine,” Charlie Brink, of the Air Force Research Laboratory at the Wright-Patterson Air Force Base in Ohio, said in a statement.
“All our data showed we had created the right conditions for engine ignition and we were very hopeful to meet our test objectives.”
The previous test aircraft was also lost to the Pacific after it was unable to restart its engine.
But the original test flight, in 2010, flew at five times the speed of sound for three minutes.
The Pentagon – which helped fund the project – has been testing hypersonic technologies in an effort to develop faster missiles.
It has also been suggested the research could eventually help build a commercial plane with the promise of London to New York trips taking as little as an hour, or Tokyo to Paris journeys slightly more than double that time.
For now only one X-51A vehicle remains and the Air Force has not yet decided whether to organize a fourth test.
The United States Air Force has launched an internal investigation after a disturbing image of 15 soldiers posing with one of them chained up in an open casket with a noose around his neck surfaced online.
The picture is dated August 23 and appeared on Facebook in early October, with the caption: “Da Dumpt, Da Dumpt… Sucks 2 Be U” scribbled on the bottom.
The image was published in the Air Force Times this week and has sparked outrage from soldiers and military wives and widows, appalled by the display.
The picture shows the group of male and female soldiers wearing fatigues crossing their arms to make “X” signs as they gather around a fellow airman who appears lifeless lying in a metal casket used to transport fallen soldiers.
The picture is dated August 23 and appeared on Facebook in early October
Air Force Times reports a former soldier who saw the photo on the social networking website forwarded it to friends, including Staff Sergeant Elias Bonilla of the 82nd Airborne Division.
Sergeant Elias Bonilla emailed the photo to Air Force Times with a note reading: “I cannot help but picture the faces of my dead [soldiers] that we drug out of burning vehicles, dug out from collapsed buildings.”
The soldiers’ names have not yet been released. However, it is believed they are “Port Dogs” who load planes, who were attending Air Transportation technical school.
Military officials said today they are from the 345th Training Squadron in Fort Lee, Virginia. Their unit is a detachment from a command at Lackland Air Force Base in Texas.
Air Force Times reported an investigation was launched after it forwarded the photo to Air Education and Training Command, the overall training command for the Air Force, for comment.
Air Force Secretary Michael Donley told the newspaper: “We take this matter seriously. [Air Education and Training Command] has initiated a commander directed investigation.
“Such behavior is not consistent with our core values, and it is not representative of the Airmen I know. It saddens me that this may cause additional grief to the families of our fallen warriors.”
David E. Smith, spokesman for the training command, told Air Force Times that the commander of the 37th Training Group at Lackland, Colonel Gregory Reese, was “obviously displeased”.
However, it was not known at press time if any charges could be brought against the soldiers, or if any rules had been violated.
The intent of the photo had not been determined at press time.
But Air Force officers and military families have made clear its message was shockingly offensive, and are calling for the troops’ dismissals.
Air Force police officer Mike Hayes, commenting on the story, wrote: “All these NCOs and Airman should be prosecuted and dismissed from the military. This is disgraceful and disrespectful to all the men.”
The investigation is expected to be completed in one to two weeks.
The shocking display comes a month after the Washington Post reported the Air Force’s mortuary at Dover Air Force Base, Delaware, had lost and mishandled the remains of hundreds of dead troops, sending them to for burial in a landfill in Virginia.
CNN reports a congressional panel investigating the actions of the Dover Air Force Base Mortuary will meet for the first time next week.