In vanilla singleplayer, If you place a tnt-minecart on a normal rail, or powered rails ... (it did it with any rails) - and if it's pushed off by hand or by powered rails ... tnt-minecarts will detonate while falling in mid air.
I thought the minecart-tnt were only supposed to explode if they went over an activator rail. So I hope this helps.
-ekl
Linked issues
Comments 3
I saw that too ... i'm meaning even if you do one at a time ... they explode on impact without being charged
Carts bumping into each other may explode.