14 CFR § 135.229 - Airport requirements.
(a) No certificate holder may use any airport unless it is adequate for the proposed operation, considering such items as size, surface, obstructions, and lighting.
(1) That pilot has determined the wind direction from an illuminated wind direction indicator or local ground communications or, in the case of takeoff, that pilot's personal observations; and
(2) The limits of the area to be used for landing or takeoff are clearly shown -
(i) For airplanes, by boundary or runway marker lights;
(ii) For helicopters, by boundary or runway marker lights or reflective material.