The US Air Force has indefinitely suspended all solo flights in T-6 Texan trainer aircraft at Columbus, Vance and Sheppard Air Bases over concerns about hypoxia and other so-called unexplained physiological events, starting from 1 February. 

The entire fleet of T-6A Texans at Vance Air Force Base in Oklahoma was grounded last November after pilots experienced hypoxia-like symptoms in four different flights. After two weeks of investigation to find the root cause of the problems, the flights resumed, although experts found no specific explanations.

Previously, the participation of T-6 aircraft in a tender for the Turkish Air Force's pilot training requirement had come into question. Some of the pilots who went to the US at that time are flying in Hürkuş' test flights.