Because of the safety considerations it is not possible to ban the use of this technique. In practice, however, it is often possible to balance the safety aspect in terms of the actual runway length available rather than in terms of a shorter length required by an aircraft operating near to its limits of performance capability. Consequently, on long runways the selection of idle rather than full reverse thrust will significantly reduce the noise, whilst ensuring that the system is immediately available in case an emergency develops. It is therefore quite proper for an ,airport to request that aircraft operators restrict the use of reverse thrust whenever safety considerations permit.