The term 'PREFIX WITH PLANE' can be solved by four different crossword solutions: AERO (4 letters), ALTI (4 letters), AQUA (4 letters), and HYDRO (5 letters). AERO is a prefix meaning air or atmosphere, ALTI is a prefix meaning high or altitude, AQUA is a prefix meaning water, and HYDRO is a prefix meaning water. Therefore, the four crossword solutions all have to do with air, altitude, water, and water respectively when combined with the word 'PLANE.'