if BA are making £800m of which £150m is out of the pocket of its employees, then would that be fair?
All profits are out of the pocket of employees. Companies (in the purest terms) employ people to make more money out of them in profit than they cost to employ. If that isn't true of a particular sector of employees, then the company must change that. To turn it the other way around, is it fair that £150 million of the current losses has gone into the pockets of one sector of staff*?
No company can base its staff costs on making a profit only when times are good.
*Not that simple of course, but it illustrates the point.