The Shulhan Aruch (Orah Haim 162:1) says that when washing Netilat Yadaim, one should raise one’s hands. This is done because the water contacting the impure hands will itself become impure and will not be able to trickle back and transmit impurity to other parts of the hand. However, if one is washing with aRevi’it (roughly 3 oz., 86 mL) or more of water however, one need not raise one’s hands, and one need only wash each hand once. Indeed, Rabbi Shalom Messas (Shu”t Shemesh Umagen, vol. 2, § 71) explains that it was the custom of many rabbis in Morocco to only wash each hand once for Netilat Yadaim. Neverthless, the Kaf HaHaim (O.H. 162:2) explains that, based on Kabbalah, each hand should be washed three times, even when using more than a Revi’it of water.
Summary: Although the common practice is to wash each hand three times for Netilat Yadaim, strictly speaking, one need wash each hand once, so long as one is using more than a Revi’it of water.