In the Sunnah there are several adhkaar which it is mustahabb for the one who wants to travel to say. These include:
It was narrated from ‘Abd-Allaah ibn ‘Umar (may Allaah be pleased with him) that when the Messenger of Allaah (peace and blessings of Allaah be upon him) mounted his camel to set out on a journey, he would say takbeer three times, then he would say: “Subhaan allathi sakhkhara lana hadha wa ma kunna lahu muqrineen wa inna ila rabbina la munqaliboon. Allaahumma inna nas’aluka fi safarina haadha al-birra wa’l-taqwa wa min al-‘aml ma tarda, Allaahumma hawwin ‘alayna safarana haadha watwi ‘anna bu’dahu. Allaahumma anta al-saahib fi’l-safar wa’l-khaleefah fi’l-ahl. Allaahumma inni a’oodhu bika min wa’tha’ al-safar wa ka’aabat al-manzar wa su’ al-munqalib fi’l-maali wa’l-ahl (Glory be to the One Who has placed this (transport) at our service and we ourselves would not have been capable of that, and to our Lord is our final destiny. O Allaah, we ask You for righteousness and piety in this journey of ours, and we ask You for deeds which please You. O Allaah, facilitate our journey and let us cover its distance quickly. O Allaah, You are the Companion on the journey and the Successor (the One Who guards them in a person’s absence) over the family. O Allaah, I seek refuge with You from the difficulties of travel, from having a change of heart and from being in a bad predicament, and I seek refuge with You from an ill-fated outcome with regard to wealth and family).” And when he returned he would say the same words, with the following addition: “Aayiboona taa’iboona ‘aabidoona li rabbina haamidoon (Returning, repenting, worshipping and praising our Lord).”