Galaxy, in my link above.
"News of the pilots' refusal to fly was first reported Tuesday night by Fox News. The outlet reported that Marine 1st Lt. Michael Pence, son of Vice President Mike Pence, is among the student pilots affected by the strike."
Lone wolf, same link.
"Fox reported that physiological episodes connected to problems with the trainers' onboard oxygen generation systems had quadrupled over the last five years, with 10 episodes in the last month. In August, the report notes, a flight instructor and student ejected near Kingsville after they both felt symptoms of hypoxia. While they both survived without injury, the aircraft crashed and was destroyed."