The Royal Air Force Mountain Rescue Service (RAFMRS) provides the UK military's only all-weather search and rescue asset for the United Kingdom. Royal Air Force mountain rescue teams (MRTs) were first organised during World War II to rescue aircrew from the large number of aircraft crashes then occurring due to minor navigational errors in conjunction with bad weather and resulting poor visibility when flying in the vicinity of high ground. The practice at the time was to organise ad-hoc rescue parties from station medical sections and other ground personnel.