A training accident involving two jets at Vance Air Force Base in Enid, Oklahoma, took the lives of two airmen on Thursday.

The two T-38 Talons were involved in what officials referred to as a “training mishap” early Thursday morning that left one plane in the grass near the AFB runway and another upside down in the dirt. The identities of the deceased airmen were not released pending notification of their families. Details about the cause of the accident were not immediately clear.