I can't see it as being illegal, it happens everyday in the public and private sector. A position is made redundant it has nothing to do with the person filling that position. I know of friends even family that have been made redundant due to the position they were filling being made redundant with them serving many years in the company.
If the jet jobs are to go then that's just the way it is.
LIFO seems the fairest but is not a legal requirement.