Point at infinity complex field, the set of points at infinity is a manifold. In artistic drawing and technical perspective, the projection on the picture plane of the point at infinity of a class of parallel lines is called their vanishing point. In hyperbolic geometry, points at infinity are typically named ideal points. Unlike Euclidean and elliptic geometries, each line has two points at infinity: given a line "l" and a point "P" not on "l", the right- and left-limiting parallels converge asymptotically to different points at infinity. All points at infinity together form the Cayley absolute or boundary of a hyperbolic plane.
Point-to-point transit or connecting flights so baggage must be collected and rechecked even to transfer between flights booked at the same time on the same airline. Although there are many point-to-point airlines, most have at least a "homebase" airport where most flights originate or depart. The United States airport system was point-to-point, controlled by CAB, until deregulation late 1960s/early 1970s, and eventually the 1978 Airline Deregulation Act when they switched to the hub concept, until the advent of low-cost carriers, when point-to-point air transport increased. Some full-service network carriers operate the point-to-point model alongside the hub-and-spoke system for certain high-density routes between