Aspects of the technology relate to a propeller blade assembly that is used in lateral propulsion systems for lighter-than-air high altitude platforms designed to operate, e.g., in the stratosphere. During operation, the propeller of the assembly is pointed along a specified heading and rotates at a selected velocity (e.g., hundreds or thousands of revolutions per minute). Power is supplied to the propeller as needed during lateral propulsion to move the platform along a particular trajectory or to remain on station over a given geographic location. In certain circumstances, the propeller may become damaged. This can include one or more blades breaking or shattering, which can result in failure of the propeller and potentially the entire LTA platform. The technology provides blades that are sufficiently flexible to avoid breakage or shattering due to debris impact or envelope entanglement, or otherwise shed a load. This can avoid catastrophic failure during stratospheric operation.