Say three times:
اَللّٰهُ أَكْبَرُ
Allah is the Most Great.
Allaahu 'Akbar
..and then say:
سُبْحَانَ الَّذِيْ سَخَّرَ لَنَا هٰذَا وَمَا كُنَّا لَهُ مُقْرِنِيْنَ، وَإِنَّا إِلَى رَبِّنَا لَمُنْقَلِبُوْنَ
Glory is to Him Who has provided this for us though we could never have had it by our efforts. Surely, unto our Lord we are returning.
Subhaanal-lathee sakhkhara lanaa haathaa wa maa kunnaa lahu muqrineen. Wa 'innaa 'ilaa Rabbinaa lamunqaliboon.
اَللّٰهُمَّ إِنَّا نَسْأَلُكَ فِيْ سَفَرِنَا هٰذَا الْبِرَّ وَالتَّقْوَى، وَمِنَ الْعَمَلِ مَا تَرْضَى، اَللّٰهُمَّ هَوِّنْ عَلَيْنَا سَفَرَنَا هٰذَا وَاطْوِ عَنَّا بُعْدَهُ، اَللّٰهُمَّ أَنْتَ الصَّاحِبُ فِي السَّفَرِ، وَالْخَلِيْفَةُ فِي الْأَهْلِ
O Allah, we ask You on this our journey for goodness and piety, and for works that are pleasing to You. O Allah, lighten this journey for us and make its distance easy for us. O Allah, You are our Companion on the road and the One in Whose care we leave our family.
Allaahumma 'innaa nas'aluka fee safarinaa haathal-birrawattaqwaa, waminal-'amalimaa tardhaa, Allaahumma hawwin 'alaynaa safaranaa haathaa watwi 'annaa bu'dahu, Allaahumma 'Antas-saahibu fis-safari, walkhaleefatu fil-'ahli,
اَللّٰهُمَّ إِنِّيْ أَعُوْذُ بِكَ مِنْ وَعْثَاءِ السَّفَرِ، وَكَآبَةِ الْمَنْظَرِ، وَسُوْءِ الْمُنْقَلَبِ فِي الْمَالِ وَالْأَهْلِ
O Allah, I seek refuge in You from this journey's hardships, and from the wicked sights in store and from finding our family and property in misfortune upon returning.
Allaahumma 'innee 'a'oothu bika min wa'thaa'is-safari, wa ka'aabanl-mandhari, wa soo'il-munqalabi fil-maaliwal'ahli.
Upon returning recite the same again adding:
آيِبُوْنَ، تَائِبُوْنَ، عَابِدُوْنَ، لِرَبِّنَا حَامِدُوْنَ
We return repentant to our Lord, worshipping our Lord, and praising our Lord.
Aa'iboona, taa'iboona, 'aabidoona, Lirabbinaa haamidoon.