The red drives have a finite supply of energy. It was also demonstrated by the mega cannon of death. It inserted a loaded red drive and emptied it in one shot, thus ejecting a dead one. So, if you use trans-am with a fake drive, you have to be mindful of the comsumption because like with a jet on afterburner, it probably consumes the fumes really fast and if you don't turn it off soon enough you won't be able to fly back to the base. The real drives just turn off the trans-am and then you can still fly with reduced capabilities until you have accumulated enough reserves to again trans-am (or just fight normally). I don't think there's anything strange here.