There is no simple division of labor between the two agencies; MI-5 usually is involved with domestic operations, and MI-6 is usually involved in overseas operations, but the real distinction is that one houses one group of agencies, and the other houses another. Like MI-5, the SIS/MI-6 was founded in 1909 as a joint operation between the Admiralty and the War Office.
During the Cold War, the agency was badly compromised by pro-Soviet staff (the "Cambridge Spy Ring"). It later recovered from Soviet penetration and recruited Col. Oleg Penkovsky.
The Mi-6 was and is one of the biggest helicopters. It was introduced in 1957. It set world records for max payload and speed in the class of helicopters. It could carry 68 troops, missiles, and even small vehicles like the BRDM. It had large wings that helped to increase speed on the sides. It used rear clamshell doors to load up.
Type: Transport Helicopter
Dimensions: span 35m; length 41.74m; height 9.86m
Range: 250km w/ max payload