The tests have been delayed repeatedly since 2017, and should have taken place this month, according to the Defense Ministry.

“The technical challenges and impact of COVID-19 have delayed the preparation of the simulation facility where the sophisticated testing of the most expensive US weapons system will take place,” said Jessica Maxwell, the spokesperson of Ellen Lord, the Defense Department’s undersecretary for acquisition and sustainment.

The F-35 was the product of the Joint Strike Fighter (JSF) program, which was the merger of various combat aircraft programs from the 1980s and 1990s.

Lockheed Martin is the prime F-35 contractor, with principal partners Northrop Grumman and BAE Systems. The aircraft has three main variants: the conventional takeoff and landing F-35A, the short take-off and vertical-landing F-35B, and the carrier-based F-35C.