I am not so sure an airline can remove staff travel privileges from a striker as long as the industrial action is legal.
Think again! It is a non contractual benefit as per below.
You will lose staff travel. If you miss any duty on your roster during the
strike, you will be banned from using staff travel permanently. This ban
covers you and all your nominees and you will not be eligible to be a
nominee on other colleagues’ staff travel. Staff travel is a
non-contractual benefit that the company is legally entitled to withdraw
from you.