Frame airline before start of hijack (4)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

A charade of SAS (Scandanavian Airlines System, ‘airline’) plus H (‘start of H ijack’). ‘Frame’ is not the first word which come to my mind for SASH, but various dictionaries define the latter as a window frame (and onelook.com even picks up from somewhere SASH as a frame for a saw in sawmilling).