Last year Bell grounded its two 525 Relentless prototypes, after the fatal crash of their third prototype on July 6 that killed both test pilots. They have now confirmed that due to this, certification for the 525s have been delayed.

The two prototypes have been under a US National Transportation Safety Board accident investigation since the crash. Their five-year certification period with the FAA has expired. They have extended it with two additional years and hope that they received certification by the end 2018, reports Flight Global.