My employer has a large volume of colleagues with flexible working patterns and compressed hours. Unfortunately due to historical demands - many of my coworkers take their non working day on Friday.
For example there are four of us that does my specific type of role- me, one who is off every Friday, and the other two are off alternating Fridays. So at best before anyone is on holiday or sick - there's only two of us in the office. Add if one of us two are on holiday leave or off sick - it's down to one of us. This means that it's becoming nearly impossible for me to take a holiday on a Friday because it'll leave just one of my colleagues in the office as the others don't work My boss declines my requests for the odd Friday afternoon off on holiday on the basis of insufficient cover yet happily has my coworkers off every Friday or every second Friday. How is this fair or reasonable?
I’m in a very similar situation. I have one colleague who doesn’t work a Friday, and one who only works Friday AM. I’m the only one in after lunchtime on Fridays. I’m not allowed to WFH on a Friday either, despite my boss doing so routinely. I am routinely told I can’t take long weekends, and had to fight to get one Friday off, so I can take almost 2 weeks off. I’m battling to get the second one off, so I can actually book a 14 day package holiday. I don’t have the answer, but I’m sending you my sympathies. It’s shit, and it’s all down to bad management approving this situation in the first place.
You can bring this up with your manager and ask for the days of the existing staff to be changed. Provided the manager gives them notice of the change they can't do anything about it - other than leave.