Ata bin Abi Rabah narrates that Sayyidah Aishah (may Allah be pleased with her) used to pray the obligatory prayers as four rak'ahs while travelling.
This is in agreement with the narration of Dalham bin Salih, although Dalham's narration has an additional link in its chain; and its chain has a strong supporting report with a sahih (authentic) chain.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 5426