I say, and with God's success: It is recommended to pray Fajr with the light of dawn, both in travel and in residence. The Prophet (peace be upon him) said: "Pray Fajr at dawn, for it is greater in reward" in Sahih Ibn Hibban 4: 357, and Jami` at-Tirmidhi 1: 289, and he said: it is good and authentic. And from Ibrahim an-Nakha'i, he said: "The companions of the Messenger of God (peace be upon him) never agreed on anything as they agreed on praying with light." In Musannaf Ibn Abi Shaybah 1: 284, and Al-Athar 1: 20, 50, and Sharh Ma'ani Al-Athar 1: 184. This is because praying at dawn increases the congregation, while praying in darkness reduces it, and what leads to an increase is better, and God knows best.