It's sunnah to say Duaa Qunoot in the last Rak^ah of Fajr prayer after ruku^, and in times of calamaties.
The Du^a' is:
اللهم اهدني فيمن هديت وعافني فيمن عافيت وتولني فيمن توليت وبارك لي فيما أعطيت وقِني واصرف عني شر ما قضيت إنك تقضي ولا يُقضى عليك وإنه لا يذل من واليت تباركت ربنا وتعاليت
Translation: O Allah, guide us along with those whom You have guided aright; and grant us well-being along with those whom You have granted well-being; and protect us with those whom You have protected. Bless for us all that You have given us; and save us and keep away from us any evil that You have decreed, for verily You decree in truth, and none can decree over You. And none is abased whom You support, and none is honored whom You oppose. Glorified are You, our Lord, Exalted.
To You, O Allah, all praise is due for what You have decreed, and to You, O Allah, is due all thanks for Your blessings and bounty. We seek forgiveness from (You) Allah, and we repent to You. We seek forgiveness from Allah, and we repent to You.
Say this Du^aa: "O Allah, forgive the Muslims, men and women". If done write (Ameen)