It is said that one should offer 2 units of prayer before departing on a journey (salat al-khuruj ila’s-safar), and upon return from the journey (salat al-‘awda).

On the authority of Maqtam ibn al-Miqdam that he said, "The Messenger of Allah (salAllahu alayhi wasalam) said, 'No one has left behind with their family anything better than two rakats offered at home when wanting travel.'"
[reported by al-Tabarani]

Kaab ibn Malik relates, "The Messenger of Allah (salAllahu alayhi wasalam) would not arrive from a journey except daytime in the forenoon, so if he arrived he started with the mosque and prayed two rakats in it then sat."
[Muslim]

Whoever desires to travel should offer two rakats of prayer in his home prior to traveling, and when he returns from his journey he should seek the mosque and offer two rakats therein.
[Radd al-Muhtar, 1:459]