out of these efforts emerged the t-4, a clean-sheet indigenously-developed trainer aircraft. according to aerospace publication flight international, it was considered plausible for the t-4 to have been a competitive product upon the global trainer aircraft market if it had been priced appropriately, but such export opportunities were denied by a long-standing japanese policy that forbids any military export sales. as such, there was no realistic prospect of the type being sold to overseas customers and it was developed for the onset with the understanding that the t-4 would be used only by the jasdf.