Group cohesion is influenced by a number of factors,most notably time,size,the prestige of the team,external pressure,and internal competition. Group cohesion evolves gradually over time through a group's normal development. Smaller groups-those of five or seven members,for example-are more cohesive than those of more than twenty-five,although cohesion does not decline much with size after forty or more members. Prestige or social status also influences a group's cohesion, with more prestigious groups,such as the U.S. Air Force Thunderbirds or the U.S. Navy Blue Angels,being highly cohesive. However,even groups of very low prestige may be highly cohesive in how they stick together. Finally,external pressure and internal competition influence group cohesion. Although the mechanics' union,pilots,and other internal constituencies at Eastern Airlines had various differences of opinion,they all pulled