The term 'Nautical Leader' can be broken down into two crossword solutions: AERO (4 letters) and ASTRO (5 letters). AERO is an abbreviation for Aeronautics, which is the science of flight and the operation of aircraft. ASTRO is an abbreviation for Astronautics, which is the science of spaceflight and the operation of spacecraft. Together, these two terms refer to a leader in the field of aeronautics and astronautics, or someone who is knowledgeable and experienced in the operation of both aircraft and spacecraft.