In the field of powered lift there is a long history of collaboration between the USA and the UK. The most obvious manisfestation of this is the Harrier/AV8 aircraft series which was preceded in the 1950's by the original Hawker P1127 Kestrel experimental aircraft. The capability of that aircraft series has now been greatly extended by the development of the AV8B/Harrier GR5, with its new wing, uprated engine and other improvements.This latest version of the concept that originated in the Kestrel is, however, still a subsonic aircraft. The operational advantages of short take-off and vertical landing combined with supersonic performance and high agility in a future combat aircraft are very attractive to both the US and UK. This interest has led to the latest US/UK powered lift collaboration designated Advanced Short Take-off and Vertical Landing (ASTOVL). This collaboration was formalised in January 1986 by a government to government Memorandum of Understanding (MOU). This paper will outline the aims and provisions of the MOU, describe the programme of design studies and technology research that has been set up under its auspices, and report on progress of the programme to date.