May not be the most palatable solution, however:
Select cell K4 and simultaneously press the Ctrl, Shift and down arrow keys (this should select K4:K278),
Press the Ctrl + c keys to copy the range,
Press the Ctrl + Alt + v keys to open the paste special dialog box
Select values and select OK
You may now sort based on the values in the 'Fleet' column.
Note that the formula has been replaced with values and would have to be reapplied to K4 and copied down if you wish to use it again.
Let us know if you have any questions.