The Pentagon temporarily grounded the entire F-35 Joint Strike Fighter fleet at the start of the weekend after one of the advanced jets suffered an engine oil leak and declared an in-flight emergency.

While the suspension of flight and ground testing on Friday was described by F-35 program officials as a precautionary move, it is the second time in 16 months that engine problems have grounded the entire fleet. It comes just two weeks before the plane is due to make its first international appearance.

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