To me this was an enormous problem with the airline's staffing co-ordination.  If their staff is going to have to be at a job somewhere that requires them to have a seat on one of their flights then why not have them booked when there are still seats available?  Why did all four have to be on the same flight?  Why not leave seats on all flights for staff rather than cause such bad p.r. for yourselves?  Greed.  Greed.  More greed makes for bad business.