Ata narrates from Sayyidah Aishah (may Allah be pleased with her) that the Prophet (peace and blessings be upon him) used to shorten the prayer while travelling and sometimes also prayed it in full, and he would fast and sometimes also break his fast.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 5425