2.8 Other Airspace — MTRs, TRSAs, NSAs, Parachute Areas, Wildlife Refuges

20 min · UA.II.A.K3

This lesson collects the airspace that is neither a lettered class nor special use airspace. None of it requires an ATC authorization. All of it can hurt you, and the exam samples from it heavily because it is where careless study shows.

Military Training Routes

A military training route (MTR) is a corridor used by military aircraft to practice low-altitude, high-speed flight. Traffic on an MTR is typically faster than 250 knots and can be as low as a few hundred feet above the ground. A fighter at 450 knots covers a nautical mile in eight seconds. You will not see it in time to react.

MTRs appear as thin gray lines with the route designator printed along the centerline. Two letters and a number tell you everything:

• IR — an IFR military training route. Flown under instrument flight rules regardless of weather.
• VR — a VFR military training route. Flown under visual rules, requiring at least 5 miles of flight visibility and a ceiling no lower than 3,000 feet AGL.

Now the digit count, which is the tested fact:

Four digits means the entire route stays at or below 1,500 feet AGL. Three digits means at least part of it goes above 1,500 feet AGL.

Count the digits after the letters, not the whole string. VR1667 has four digits, so that route is flown entirely at or below 1,500 feet AGL — squarely in the altitude band a drone occupies. IR206 has three, so somewhere along it the aircraft climb higher. Either way the route can and does contain traffic below 1,500 AGL, so an MTR crossing your job site deserves a phone call.

Contact Flight Service within 100 nautical miles of an MTR for current route activity and scheduled use times. Call 1-800-WX-BRIEF or ask during an online briefing. The route status is not on the chart, only the route itself.

Terminal Radar Service Areas

A TRSA is a leftover from an older system. It surrounds certain airports where radar service is offered to VFR traffic, but the airspace was never converted to Class B or C. The primary airport inside a TRSA is Class D.

TRSAs are charted with a screened black outline with altitude segments labeled. Participation is voluntary even for manned VFR pilots, and a TRSA is not one of the airspace classes listed in §107.41. A TRSA requires no ATC authorization for a Part 107 flight. The Class D at its center does.

National Security Areas

A National Security Area (NSA) is airspace over a ground facility that needs extra security and safety — a weapons plant, a naval facility, a laboratory. It is charted with a broken (dashed) magenta line and labeled with its altitude and a note.

Pilots are requested to voluntarily avoid flying through an NSA. It is a request, not a prohibition — unless the FAA issues a NOTAM temporarily prohibiting flight under 14 CFR §99.7. When that happens, the prohibition is enforceable, and you find out about it by checking NOTAMs, which is the only way you find out about anything temporary.

Note the depiction carefully: dashed magenta again, but around a *facility* and labeled NSA, not around an airport. Context separates it from a Class E surface area.

Parachute jump areas

Charted with a parachute symbol and often a frequency, these mark airports and sites with regular jump operations under 14 CFR Part 105. Jump altitudes are given in MSL. Jump aircraft broadcast their intentions on the CTAF, and canopies descend far faster than they look like they are descending.

Nothing prohibits a Part 107 flight near a charted jump area, but a parachutist under canopy is not going to see or avoid your aircraft. Monitor the CTAF, and pick a different day if jumping is in progress.

Wildlife refuges, parks and wilderness areas

Sectionals chart National Parks, National Monuments, National Wildlife Refuges, and Primitive and Wilderness Areas with a distinctive boundary and the area's name. Two separate rules apply, and they get conflated constantly.

1. The airspace advisory. AIM 7-5-6 states that pilots are requested to maintain a minimum altitude of 2,000 feet above the surface of these areas. The word in the AIM is *requested*. It is an advisory aimed at protecting wildlife and visitors, not a regulation, and a Part 107 pilot capped at 400 feet AGL cannot comply with it anyway.
2. The ground rule. The National Park Service separately prohibits launching, landing or operating unmanned aircraft from or on lands and waters it administers, under its closure authority in 36 CFR §1.5. That is enforceable, and it is about the ground, not the air. The FAA controls the airspace; the land manager controls the dirt.

The practical translation for a working drone pilot: you may not set up in a national park, but you may set up legally outside the boundary. The US Fish and Wildlife Service and the US Forest Service each have their own land-use rules, and the AIM also notes that landing an aircraft on NPS, FWS or Forest Service land requires that agency's authorization.

Airport advisory services and published VFR routes

Two smaller items round out the list. Local Airport Advisory (LAA) is a Flight Service product available in Alaska at certain non-towered airports with a Flight Service Station on the field, providing advisories within 10 statute miles. Remote Airport Information Service (RAIS) supports short-term special events and is advertised by NOTAM only.

Published VFR routes help manned pilots move around busy airspace. VFR flyways are suggested paths that avoid Class B. VFR corridors are defined tunnels through Class B that need no clearance. VFR transition routes are charted courses through Class B that do require ATC clearance. They appear mainly on Terminal Area Charts. A corridor does not create a Part 107 exception — if you are inside the lateral and vertical limits of Class B, §107.41 applies regardless.