In Europe the Single European Sky air traffic management master plan foresees the introduction of several modern digital data links for aeronautical communications. The candidate for long-range continental communications is LDACS. LDACS is a cellular, ground-based digital communications system for flight guidance and communications related to safety and regularity of flight. Hence, the aeronautical standards for cybersecurity of the link layer and the network layer apply. In previous works, threat- and risk analyses of LDACS were conducted, a draft for an LDACS cybersecurity architecture was introduced, algorithms proposed, and the security of the Station-to-Station (STS)-based Mutual Authentication and Key Establishment (MAKE) procedure of LDACS formally verified. However, options for cipher-suites and certificate management for LDACS are still missing. This paper proposes a cell-attachment procedure, which establishes a secure LDACS communication channel between an aircraft and corresponding ground-station upon cell-entry of the aircraft, that addresses these shortcomings. It introduces a full cell-attachment protocol including ciphersuites and certificate revocation for LDACS.