Mobility-as-a-Service (MaaS) is an advanced Intelligent Transport System (ITS) that integrates various modes of transportation to meet the demands of travellers. The system relies on frequent communication for data exchange between the MaaS provider and transport service providers. Ideally, such communication would utilize trust technologies between these entities. However, current MaaS systems lack transparency and reliability, and their centralized nature creates a single point of failure for the entire service. To address these issues, this paper proposes a blockchain-based MaaS, which includes an architecture and smart contract functionalities. The solutions are built on permissioned and permissionless Hyperledger Fabric and Ethereum blockchain platforms, respectively, for a realistic deployment of network architecture and proposed smart contracts. Additionally, the paper presents a framework derived from comparing these two blockchain platforms. Finally, the framework is evaluated, and open questions and challenges are analysed.