What maneuvers are permitted in ET (I)?

In the context of formation flying, especially involving ET (Extended Tactics) maneuvers, stable turns are permitted because they allow the formation to maintain position and spacing while changing heading. Stable turns ensure that all aircraft in the formation are able to maintain their relative positions without excessive turbulence or loss of control, which is critical for safety and effectiveness during formation flight.

Other options involve maneuvers that introduce greater risk or complexity during formation flying. For instance, stabilized climbs can be challenging in formation due to differing power settings and climb rates among the aircraft. Vertical loops and high-speed passes, on the other hand, can lead to dramatic changes in energy state and position, making it difficult for the formation to remain cohesive and coordinated. Thus, while they may be fun or impressive, these maneuvers are not suitable for the controlled and precise environment required in formation flying.