Radix is closest. Under FAA rules (119.1) if a person or business supplies both a pilot and an aircraft to a customer they are an air carrier and require an air carrier operating certificate.
pattern_is_full's answer misses the operating certificate, in this case (small airplane) a part 135 certificate. I'm not quite sure what he means by CF license. In order to be compensated for their services pilots must hold a commercial pilot certificate. The FAA has even held that a private pilot flying for "free" is being compensated with hours logged toward a higher rating.