A total of approximately 4000 Catalinas were built between 1936 and 1945. Because of their worldwide popularity, there was scarcely a maritime battle in WW II in which they were not involved. The PBY had its vulnerabilities: it was slow, with a maximum speed of 179 mph, and with no crew armor or self-sealing tanks, it was highly vulnerable to anti-aircraft attack. However it was these weaknesses, coincident with the development of effective radar, and Japanese reliance on night transport, which led to the development of the "Black Cat Squadrons." These crews performed nighttime search and attack missions in their black-painted PBYs. The tactics were spectacularly successful and seriously disrupted the flow of supplies and personnel to Japanese island bases. The Catalinas also proved effective in search and rescue missions, code-named "Dumbo." Small detachments (normally of three PBYs) routinely orbited on stand-by near targeted combat areas. One detachment based in the Solomon islands rescued 161 airmen between January 1 and August 15, 1943, and successes increased steadily as equipment and tactics improved. After WW II, the PBY continued its search and rescue service in many Central and South American countries, as well as in Denmark, until the 1970's.