Gap GeoTek has developed a high resolution helicopter-borne magnetic acquisition system that is suitable for larger scale surveys - such as 50 square kilometres or more. It is well suited to perform Sub-Audio Magnetics surveys, using the standard wire and transmitter setup as for a ground survey. The sensor is located within a towed bird, which can be fitted to any helicopter with a tow hook.
See here for further detail on the helicopter system. The receiver system has been setup to have a small volume and weight so as to be easily accommodated into small helicopters.
Available below is a brochure outlining a comparison between a ground based and air based SAM survey.