A modular vehicle system comprising: - at least one body module (100; 1100) comprising at least one body connection interface; - a kit comprising a plurality of utility modules including at least one first utility module and at least one second utility module, each said first utility module being in the form of a fixed-wing utility module configured for selectively providing said at least one body module (100; 1100) with fixed wing flight capability when coupled thereto, each said first utility module comprising at least one utility module connection interface in the form of a first utility module connection interface for coupling with at least one said body connection interface to thereby enable coupling of the respective said first utility module to the said at least one body module; each said second utility module being in the form of a rotor-wing utility module configured for selectively providing said at least one body module (100; 1100) with rotor wing flight capability when coupled thereto, each said second utility module comprising at least one said utility module connection interface in the form of a second utility module connection interface, distinct from said first utility module connection interface, for coupling with at least one said body connection interface to thereby enable coupling of the respective said second utility module to the said at least one body module; - wherein each said body connection interface is configured for selective reversible coupling at least with respect to any one of said utility module connection interfaces (600, 700) while concurrently excluding coupling of another said utility module connection interface thereto, to provide an air vehicle and characterized in that each said body connection interface is further configured as a body-to-body connection interface, to enable providing at least air vehicle configurations (2FW; 2RW; 4FW; 4RW) comprising at least two said body modules (100; 1100) and comprising said at least one fixed wing utility module or said at least one rotor wing utility module. - at least one body module (100; 1100) comprising at least one body connection interface; - a kit comprising a plurality of utility modules including at least one first utility module and at least one second utility module, each said first utility module being in the form of a fixed-wing utility module configured for selectively providing said at least one body module (100; 1100) with fixed wing flight capability when coupled thereto, each said first utility module comprising at least one utility module connection interface in the form of a first utility module connection interface for coupling with at least one said body connection interface to thereby enable coupling of the respective said first utility module to the said at least one body module; each said second utility module being in the form of a rotor-wing utility module configured for selectively providing said at least one body module (100; 1100) with rotor wing flight capability when coupled thereto, each said second utility module comprising at least one said utility module connection interface in the form of a second utility module connection interface, distinct from said first utility module connection interface, for coupling with at least one said body connection interface to thereby enable coupling of the respective said second utility module to the said at least one body module; each said first utility module being in the form of a fixed-wing utility module configured for selectively providing said at least one body module (100; 1100) with fixed wing flight capability when coupled thereto, each said first utility module comprising at least one utility module connection interface in the form of a first utility module connection interface for coupling with at least one said body connection interface to thereby enable coupling of the respective said first utility module to the said at least one body module; each said second utility module being in the form of a rotor-wing utility module configured for selectively providing said at least one body module (100; 1100) with rotor wing flight capability when coupled thereto, each said second utility module comprising at least one said utility module connection interface in the form of a second utility module connection interface, distinct from said first utility module connection interface, for coupling with at least one said body connection interface to thereby enable coupling of the respective said second utility module to the said at least one body module; - wherein each said body connection interface is configured for selective reversible coupling at least with respect to any one of said utility module connection interfaces (600, 700) while concurrently excluding coupling of another said utility module connection interface thereto, to provide an air vehicle and characterized in that each said body connection interface is further configured as a body-to-body connection interface, to enable providing at least air vehicle configurations (2FW; 2RW; 4FW; 4RW) comprising at least two said body modules (100; 1100) and comprising said at least one fixed wing utility module or said at least one rotor wing utility module.