from the ground, it can be difficult for the casual observer to distinguish between the two types of aircraft in instances where the PPG is using a rolling airframe (also called a cart, trike, or quad, depending on the configuration). In simple terms, PPCs are always controlled using steering bars pushed on by the feet to operate the steering controls, and the airframe is an integral component of the aircraft (as established by-design in the FAA PPC Flying Handbook). PPGs, on the other hand, almost exclusively steer using the hands to pull on the steering lines. When paragliding, an airframe is considered purely a higher end option; in fact, since a PPG wing is always to be attached to the harness, if the airframe used in a PPG failed in any way, the wing would continue to support the weight of the occupants and motor through the harness. In addition, because PPGs use smaller low-power engines to stay within 14 C.F.R. § 103 regulations, they frequently use a higher performance parafoil that visually appears thinner and more elliptical to compensate. Any other distinctions are less clear. In the United States, all paragliding equipment must fall within 14 C.F.R. § 103, and pilot licensing (in the strict legal sense) is not applicable, which is not much different from ultralight PPCs. Other lines are blurred further. For example, some people previously argued that two-seat flying is only allowed using a PPC, but "tandem" (two-seat) paragliding is readily doable in many countries throughout the world, and limited types of tandem paragliding are legally authorized in the U.S. as a result of an FAA exemption for flight training only (since 2018, with subsequent extensions). With advances in lightweight material design, another contributing reason for confusion nowadays comes from the fact that some aircraft and kit builders market ultralight-class rolling airframes that can be configured with either PPG-style hand steering or PPC-style foot steering (along with wider canopy attachment points), with the later sold as a 14 C.F.R. § 103 'powered parachute'. The net result is nearly identical aircraft, albeit with different steering systems and potentially different canopy types. Safety PPCs are often considered to be safer than normal fixed-wing aircraft because of their inherent stability, limited response to control inputs, and stall resistance. There are two primary means to control a PPC: increasing or decreasing engine power (which controls the vertical rate of climb)