The Ministry of Defence (MoD) has objected to plans to build a zip wire across Thirlmere, in the Lake District National Park.
In a letter written to the Lake District National Park Authority, the MoD said that the zip wire would pose a risk to low flying operations frequently carried out in the area.
This is primarily due to the fact that military aircraft are unable to identify and avoid wires.
The plans were proposed by a company named Treetop Trek, who wish to create an activity area in the Lake District.
The company released a statement expressing their surprise at the MoD’s decision:
"We have been in consultation with the MoD since June 2017 and are in receipt of their written confirmation that they would not be objecting to the Thirlmere project.
“We are therefore very surprised by this apparent change in stance and are currently seeking their further clarification."
However, a spokesman from the MoD said:
"The proposed cable in this location poses a risk to low flying operations, due to military aircraft not being able to readily identify wires or safely navigate away from them."
"Competent and confident flying at low level is an essential skill for our aircrews, with valley flying being one of the most demanding elements.
"Therefore this application could cause a significant hazard and would significantly impact upon vital military training."
Proponents of the zip wire project, which would reportedly cost around £1.8m, said it would bring a major boost to the area's economy.
The national park's authority will decide later in the month whether the planning application will proceed.