Yes powder baby formula can be brought onto the plane to feed your baby with and you can ask the flight attendant for some water to mix the baby formula with if you need some water.
Or you can bring some frozen bottled water onto the plane and then use the frozen bottled water after it thaws out to make the baby formula with.
You can also bring some liquid baby formula in sealed containers onto the plane with you as well to feed the baby and I find it much easier to just bring the pre made liquid baby formula onto the plane than the powder form baby formula.
It's less mess and easier to just pour the formula into the baby bottle to feed the baby with.