Helicopter tours have been buzzing too close to Montezuma Castle National Monument/Kurt Repanshek file

It was roughly a millennium ago that the Sinagua people were attracted to a cliff face in today's central Arizona and built the equivalent of a high-rise some 100 feet off the valley floor. They knew what they were doing; they had protection from the elements, the south-facing dwelling was warmed in winter by the sun, and the height provided a great perspective of the surrounding landscape.

Down below, Beaver Creek provided a reliable source of water, and the fertile soils enabled them to cultivate corn, beans and squash, along with cotton that they turned into thread for weaving clothes. And the sycamore trees that grew along the creek were handy building materials that went into the dwellings.

The Sinagua constructed their five-story home out of limestone, mud mortar, and beams from those sycamore trees. For some reason, the site was abandoned around 1425. While the site was looted and damaged in the late 1800s, in 1897 the Arizona Antiquarian Association repaired as much as it could. In 1906, President Theodore Roosevelt designated the site Montezuma Castle National Monument.

While the large majority of today's visitors to the monument drive up to the parking area, lately there has been an uncomfortable number of helicopter tours that have threatened the integrity of the cliff dwelling. In early May, one helicopter flew down and hovered practically level with the cliff dwelling.

"We have photos of it, and from what we can tell it's somewhere around about 100 feet from the cliff dwelling, and very low, so just right above the treetops," said monument spokesperson Matt Guebard during a phone call on Thursday. 

While the helicopter company could be identified from the photo, Guebard said park personnel were withholding that information and the photo while the matter was taken up with the company. 

According to Guebard, vibrations from the chopper's rotors could damage the cliff dwelling.

"The pilots were risking serious damage to the site’s ancient architecture," he wrote in a release Wednesday. "Studies show that rotor vibrations from close-flying helicopters can cause serious problems. At Montezuma Castle, these vibrations could easily damage or destroy 850-year-old wooden ceilings and masonry walls."

In May and June there have been two such helicopter incidents, the spokesperson said.

"We've had issues with flyovers before, but as far as I know we've never had anything quite this brazen," said Guebard, who has worked at the monument for a dozen years. "We've had helicopters fly through the canyon, we've had them hover farther away, but I'm not aware of them coming in that close."

For years the FAA and the National Park Service have struggled to get on the same page when it came to managing air tours. Earlier this year, a federal court, noting that the two agencies have failed for 19 years to develop air tour management plans for national parks, ordered the agencies to get the work done.

It was 20 years ago that the National Park Air Tour Management Act of 2000 was implemented and required the FAA, in coordination with the NPS, to set limits on overflight numbers, timing, and routes to protect park resources and the visitor experience.

While the judges' ruling affected 23 units of the National Park System, Montezuma Castle was not covered by the order.

"If there is damage that is caused by the helicopters, that is something that we can pursue," Guebard said. "One of the reasons we wanted to put that press release out is we wanted to make sure helicopter companies and the public understand that there's a real potential for damaging these places, either catastrophically, or cumulative damage over time.

"Even if a helicopter flies in front of Montezuma Castle and nothing collapses, if that happens enough times then those rotor vibrations will cause cumulative damage, that can be a real issue in the future," he explained. "It's something that's really concerning for us."

Park staff did climb up to check cliff dwelling for damage but didn't detect any.

There have been efforts between the National Park Service and officials and air tour companies in nearby Sedona to come up with a voluntary agreement regarding 'no-fly' and minimum altitude zones, but not all the tour companies participated, according to the Park Service.

At the National Parks Conservation Association, Kevin Dahl said the problem of helicopters buzzing close to Montezuma Castle is not new.

"It’s great that tour companies and others in Sedona have reached a voluntary agreement because that has been the origin of most of the traffic that swoop down too close to the fragile artifacts that everyone wants to see," said Dahl, NPCA's Ariona senior program manager. "I hope it works, but if it doesn’t the next step is for FAA to work with the Park Service to enact a no-fly zone along with strict penalties for those who continue to violate these precious public resources for private gain."