the model on any "exterior-viewable" part of the model that requires nothing to be opened the modeler's registration code is personal for their use, and any number of model aircraft that they own and operate can bear the same registration code. Federal Communications Commission Licensed amateur radio operators in the United States are expressly allowed to use amateur radio frequencies for telecommand of model aircraft, per FCC Part 97's rule 97.215. However, the Federal Communications Commission prohibits using amateur radio frequencies for commercial activity (generally any form of economic gain or for-profit activity, Part 97's rule 97.113). The FCC has not yet addressed the issue of creating designated command and control frequencies for commercial unmanned aircraft, and many civilian unmanned aircraft continue to use amateur radio frequencies, even when used for commercial purposes. Though it has not so far pursued any enforcement actions related to use of amateur radio frequencies for commercial unmanned aircraft (with the FCC, as early as 1997, commencing the authorization of specific "industrial/business" frequency bands, potentially usable for such needs), the FCC has the authority to levy civil forfeitures and fines into the tens of thousands of dollars for violations of its regulations. There is no similar "displayed registration code" requirement as yet from the FCC, to that of the FAA as mentioned above (the FAA's "pilot registration code" must be on the model already), for FCC-licensed amateur radio operators flying RC aircraft under part 97.215. Since mid-July 2000, FCC Amateur Radio Service licensees have already been assigned a ten-digit "FCC registration number" or "FRN" directly linked to their callsign which could additionally be placed on their models along with any already-assigned FAA registration code, if desired. The July 2000 announcement of the "FRN" code system was partly worded: ..."The use of the registration number is voluntary, although the Commission will consider making it mandatory in the future.", leaving its use open for any future FCC-administered Amateur Radio Service needs in the United States. National Park Service Under a 2014 edict from the National Park Service, model aircraft and other unmanned aircraft operations are prohibited on all land administered by the National Park Service, with some exceptions for preexisting model aircraft fields that were established prior to the adoption of this rule. Because the National Park Service does not have jurisdiction over airspace, which is exclusively governed by the FAA, this rule only applies to unmanned