Wheels were down, flaps fully extended on final into BWI, pilot started doing S turns about 2000 AGL. I told my wife, this is not normal as the turns were GA like, very distinct maneuvers.
Next thing you know, engines spool up and pilot makes a sharp right. After we were facing the Chesapeake Bay, pilot came on and said a plane cut in front of us and due to loss of spacing we aborted the landing, but everything is ok!
I could imagine somebody on the airways getting the "call the tower instructions" after this happened.
The S turns happen a lot into O'Hare. Give the ATC a listen and you can hear the tower/PIC asking for an "S turn for spacing" quite frequently.
Same here in Vegas, but mainly for arrivals on 25L, as they have the room to the south for the S turn. If it can't be done on their arriving runway (1s, 19s, 25R), ATC may change them to another runway, more than likely the parallel.