Is it permitted to use thrust reversers in flight?

Using thrust reversers in flight is not permitted for several critical safety and operational reasons. The primary purpose of thrust reversers is to provide additional deceleration during landing by redirecting engine thrust forward, which is effective when the aircraft is on the ground. Engaging thrust reversers while airborne could lead to a significant loss of control due to the sudden and uneven change in thrust direction, potentially resulting in an uncontrollable yaw or roll.

Moreover, the design and operation of thrust reversers are such that they are not meant to withstand aerodynamic forces encountered in flight. Using them in flight could damage the engines or thrust reverser systems, leading to both safety and maintenance concerns.

Thus, the consensus established in aviation operation and safety regulations is that thrust reversers should only be utilized on the ground during landing or taxiing to enhance braking efficiency.