[1] The very next year, 1969, the design was refined, with a three-inch stretch of the fuselage, five more gallons of fuel capacity, and a 40-pound increase in gross weight.

[1] In 1975, the plane was offered with a package of equipment enabling flight into known icing conditions.

[1] In 1976, the 421C appeared which featured wet wings, the absence of wingtip fuel tanks and landing gear that was changed from straight-leg to a trailing-link design from the 1981 model year onwards.

The cabin is accessed from a door, on the left hand side behind the wing, and has seating for six on the basic 421, or up to ten on later variants.

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