An aircraft system (10, 200) comprising: an eVTOL aircraft (12, 202, 300, 400) including one or more onboard batteries (28, 204, 320, 402), the eVTOL aircraft (12, 202, 300, 400) having a vertical takeoff and landing flight mode including a landing phase; and an external power assist system (32, 214, 326) configured to selectively provide power to the onboard batteries (28, 204, 320, 402) of the eVTOL aircraft (12, 202, 300, 400), the external power assist system (32, 214, 326) comprising: a subsurface power source (34, 216, 330); and a power transfer interface (36, 218, 328) electrically coupled to the subsurface power source (34, 216, 330), the power transfer interface (36, 218, 328) movable between a plurality of positions including a deployed position and a stowed position; wherein, the power transfer interface (36, 218, 328) is configured to transfer power to the onboard batteries (28, 204, 320, 402) of the eVTOL aircraft (12, 202, 300, 400) in the deployed position; wherein, the power transfer interface (36, 218, 328) is movable at least partially subsurface in the stowed position; wherein, the eVTOL aircraft (12, 202, 300, 400) comprises a power transfer port (40, 210, 322) configured to couple to the power transfer interface (36, 218, 328) in the deployed position; and wherein, the power transfer interface (36, 218, 328) is movable along a landing surface (30, 222, 332) in the deployed position to align with the power transfer port (40, 210, 322) of the eVTOL aircraft (12, 202, 300, 400) in the landing phase of the eVTOL aircraft (12, 202, 300, 400). an eVTOL aircraft (12, 202, 300, 400) including one or more onboard batteries (28, 204, 320, 402), the eVTOL aircraft (12, 202, 300, 400) having a vertical takeoff and landing flight mode including a landing phase; and an external power assist system (32, 214, 326) configured to selectively provide power to the onboard batteries (28, 204, 320, 402) of the eVTOL aircraft (12, 202, 300, 400), the external power assist system (32, 214, 326) comprising: a subsurface power source (34, 216, 330); and a power transfer interface (36, 218, 328) electrically coupled to the subsurface power source (34, 216, 330), the power transfer interface (36, 218, 328) movable between a plurality of positions including a deployed position and a stowed position; a subsurface power source (34, 216, 330); and a power transfer interface (36, 218, 328) electrically coupled to the subsurface power source (34, 216, 330), the power transfer interface (36, 218, 328) movable between a plurality of positions including a deployed position and a stowed position; wherein, the power transfer interface (36, 218, 328) is configured to transfer power to the onboard batteries (28, 204, 320, 402) of the eVTOL aircraft (12, 202, 300, 400) in the deployed position; wherein, the power transfer interface (36, 218, 328) is movable at least partially subsurface in the stowed position; wherein, the eVTOL aircraft (12, 202, 300, 400) comprises a power transfer port (40, 210, 322) configured to couple to the power transfer interface (36, 218, 328) in the deployed position; and wherein, the power transfer interface (36, 218, 328) is movable along a landing surface (30, 222, 332) in the deployed position to align with the power transfer port (40, 210, 322) of the eVTOL aircraft (12, 202, 300, 400) in the landing phase of the eVTOL aircraft (12, 202, 300, 400).