Croydon Travel offers the overflights from Australia. They run about 4-6 flights a year.

http://www.antarcticaflights.com.au/

The overflights are on Qantas Airways Boeing 747-400 aircraft and last approximately 11-12 hours in duration. You can expect to spend 8 hours flying to and from Antarctica (4 hours each way), which leaves about 4 hours to fly over the continent.

The flight does not land, and must maintain a minimum altitude of 10,000 feet above sea level. The flight itineraries primarily operate along the northern Victoria Land coast, and the Oates, George V and Adélie Coasts. The pilots also avoid known penguin colonies to prevent disruption to wildlife.

Flights depart from Sydney, Melbourne and Adelaide. Since the flight returns to where it departed, it’s a domestic flight. Ticket pricing is based on class of travel, and there is a rotation of seating during the flight so that everyone gets a chance at a window seat. Also, there are lectures during the flight. Service includes two meals and complimentary drink service.

Lan Chile and Aerovias DAP operate overflights from Punta Arenas, as well as, landings on the South Shetland Islands. These flights are usually in conjunction with cruise trips.