14 CFR §45.27

1. (a)Rotorcraft. Each operator of a rotorcraft must display on that rotorcraft horizontally on both surfaces of the cabin, fuselage, boom, or tail the marks required by § 45.23.
2. (b)Airships. Each operator of an airship must display on that airship the marks required by § 45.23, horizontally on—
   1. (1)The upper surface of the right horizontal stabilizer and on the under surface of the left horizontal stabilizer with the top of the marks toward the leading edge of each stabilizer; and
   2. (2)Each side of the bottom half of the vertical stabilizer.
3. (c)Spherical balloons. Each operator of a spherical balloon must display the marks required by § 45.23 in two places diametrically opposite and near the maximum horizontal circumference of that balloon.
4. (d)Nonspherical balloons. Each operator of a nonspherical balloon must display the marks required by § 45.23 on each side of the balloon near its maximum cross section and immediately above either the rigging band or the points of attachment of the basket or cabin suspension cables.
5. (e)Powered parachutes and weight-shift-control aircraft. Each operator of a powered parachute or a weight-shift-control aircraft must display the marks required by §§ 45.23 and 45.29(b)(2) of this part. The marks must be displayed in two diametrically opposite positions on the fuselage, a structural member, or a component of the aircraft and must be visible from the side of the aircraft.