Horizon science of graphical perspective. Assuming the picture plane stands vertical to ground, and "P" is the perpendicular projection of the eye point "O" on the picture plane, the horizon is defined as the horizontal line through "P". The point "P" is the vanishing point of lines perpendicular to the picture. If "S" is another point on the horizon, then it is the vanishing point for all lines parallel to "OS". But Brook Taylor (1719) indicated that the horizon plane determined by "O" and the horizon was like any other plane: The peculiar geometry of perspective where parallel lines converge in
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