The present invention relates to a method of flying safely and at low altitude in an aircraft, in which method unsafe relief (R0) of terrain is determined as is the position of at least one high point (4, 5) representing an obstacle (4′, 5′) overlying said unsafe relief (R0). A main volume (V0) is added to said unsafe relief (R0), the main volume being defined between a main volume base (2) placed on the unsafe relief (R0) and an envelope (1), thereby obtaining safe relief (R1) for overflying that contains at least said unsafe relief (R0) and said main volume (V0), said main volume base (2) having an area (2′) defined by a closed peripheral curve (3) resting on said unsafe relief (R0), said envelope (1) being generated using a moving segment (S) of predetermined length (L) extending from said high point (4, 5) to a second point (3′) moving along said peripheral curve (3).