Charlotte Douglas International Airport an aviation library with over 9,000 volumes and a very extensive photography collection. Rare aircraft in the collection include one of only two surviving Douglas D-558 Skystreak aircraft and the second (and oldest surviving) U.S.-built Harrier, which was used as the flight-test aircraft and accumulated over 5,000 flight-test hours. In January 2011, the museum acquired N106US, the US Airways Airbus A320 ditched by captain Chesley Sullenberger as US Airways Flight 1549 in the Hudson River on January 15, 2009. This aircraft, which was delivered on June 10, 2011, is about 35 years younger than any other commercial airliner on display
Flock (birds) success rate when attacking the flock, rather than increasing the ability of the flock to spot an approaching predator. By birds co-existing with one another in a flock, less time and energy is spent searching for predators. This mutual protection of one another within the flock is one of the benefits to living within a group. However, as flock numbers increase the more aggressive individuals within the flock become towards one another. This is one of the costs to living within a flock. It is often seen that flocks are dynamic and thus fluctuate in size depending on the needs