Answered by Shaykh Faraz Rabbani
If there is one minute or so left till the end of fajr do you start the prayer?
Walaikum assalam,
As you know, the Fajr prayer becomes invalid once the sun rises (=before the appearance of any part of its orb above the actual horizon). As such, in the above case, you would have to quickly pray such that you finish before the sun rises. If needed, you would have to leave all sunnas and even wajib acts if it comes down to it.
Wassalam,
Faraz.