Answer:
production at this point is technically inefficient.
Step-by-step explanation:
Efficient production processes requires a producer to either minimise the inputs they are using at a given output or maximise output level at a given input level.
Technical inefficiency is when input is not minimised or output maximised.
In the given instance the fixed cost (airplane) remains unchanged. However crew members can be variable.
If the airplane only requires 3 crew members and 4 crew members are now used, the company is not minimising inputs used so they are technically inefficient.