Definition
Unmanned balloons anchored to the ground by a cable or line, often used for advertising, research, or surveillance. Because they extend into the air on a long, often hard-to-see cable, the FAA designates the airspace around larger or higher tethered balloon operations as a hazard to flight, and pilots are expected to avoid them. Operations involving balloons over 150 feet above the surface generally require notification and may be charted or published in a NOTAM.
Plain English
Balloons that are tied to the ground by a cable. The balloon and its cable are both hazards to aircraft, so pilots need to know where they are and stay clear.
Context Anchor
Seen in discussions of other airspace areas, temporary flight hazards, outdoor events, and low-altitude operations near parks, stadiums, festivals, or test sites.
Derivation
Tether comes from the Old Norse word for a rope or chain used to tie an animal so it can only move within a limited area. A tethered balloon is held in place by the same idea: a line keeping it from drifting away.
Why Pilots Care
They create tall, stationary obstacles that can reach several hundred feet and must be avoided during flight planning and low-altitude operations.
Grounding Statement
Picture a large balloon above a field with a long cable running down to the ground; an aircraft must stay clear of the entire setup.
Intuition Check
Do not assume tethered balloons are small party balloons. In aviation, tethered balloons can be large, high enough to affect aircraft, and dangerous because of the line attached to them.
Example Sentence 1
Before the cross-country flight, the pilot reviewed NOTAMs and noted a tethered balloon operation rising to 2,000 feet along the planned route.
Example Sentence 2
A NOTAM warned of tethered balloons operating up to 500 feet AGL near the practice area.