26 USC 4281 - Small aircraft on nonestablished lines

The taxes imposed by sections 4261 and 4271 shall not apply to transportation by an aircraft having a maximum certificated takeoff weight of 6,000 pounds or less, except when such aircraft is operated on an established line. For purposes of the preceding sentence, the term maximum certificated takeoff weight means the maximum such weight contained in the type certificate or airworthiness certificate. For purposes of this section, an aircraft shall not be considered as operated on an established line at any time during which such aircraft is being operated on a flight the sole purpose of which is sightseeing.