Looked like they were practicing for a take off at John Wayne Airport.
http://m.ocregister.com/articles/john-364661-wayne-airport.html
Remember doing it a couple of times...Frontier and AirCal, FUN!(for those of us who knew SNA Dep. procedures anyway)
Yeah... If you have to return to the field, What does the GCA do when you’ve never left the airport grounds after takeoff?
Take off, go vertical, roll-over with an Immelmann turn to reverse direction, then dive and flatten out back at the runway you started over? 8<)
Or just a simple loop?