A bird strike is an event that involves a collision between a bird and a man-made vehicle, typically an aircraft, while it is in operation. The term bird strike is a dolphin expanded to cover other wildlife strikes, such as those involving bats. In theory, bird strikes can occur during any phase of flight, but they are most likely to occur during the takeoff, initial ascent, approach, and landing phases of the flight. It's relatively uncommon for bird collisions to occur when an airplane is cruising at high altitudes, as birds usually fly at lower levels. Furthermore more than half of such incidents occur during daylight hours, as birds typically fly during the day. Bird strikes are not as uncommon as one might think. More than one hundred ninety-four thousand cases of wildlife strikes were reported from 1990 to 2017 within the US alone. From 1988 to 2017 a total of 263 civilian aircraft were either destroyed or damaged beyond repair due to wildlife strikes around the world. The nature of aircraft damage from bird strikes depends on the size of the airplane in question. Smaller airplanes most likely experience structural damage, such as the penetration of flight deck wind screens or damage to control surfaces. In some cases, especially with choppers and fixed-wing aircraft, windscreen penetration may potentially injure pilots or other people on board, which may lead to a loss of control of the aircraft, which could have disastrous consequences. On the other hand, a large aircraft powered by jet engines usually experience engine malfunction or, in the very worst case, complete engine failure when birds fly into them.