Definition
Forecasts issued by the National Weather Service to alert pilots in flight to potentially hazardous weather. They are broadcast and made available through Flight Service and include AIRMETs (less severe), SIGMETs (severe and widespread), and Convective SIGMETs (thunderstorm-related). Each advisory describes the type of hazard, the area affected, and the time period it covers.
Plain English
Weather warnings issued to pilots while they are flying, telling them about dangerous weather like icing, turbulence, low visibility, or thunderstorms in a specific area for a specific time.
Context Anchor
Pilots may receive inflight advisories from air traffic control, flight service, or onboard weather displays while they are en route.
Derivation
"Inflight" because these advisories are aimed at pilots already airborne (or about to be), and "advisory" from Latin advisare, to consider or take counsel — a notice meant to inform a decision rather than issue an order.
Why Pilots Care
They allow pilots to avoid or prepare for weather that can cause loss of aircraft control or force an unplanned diversion.
Intuition Check
Do not read advisory as casual or unimportant. An inflight advisory may not be a direct order, but it can contain safety-critical weather information the pilot needs to act on.
Example Sentence 1
Before descending into the valley, the pilot checked for any inflight advisories and saw an AIRMET for moderate icing below 9,000 feet.
Example Sentence 2
We adjusted our route after receiving inflight advisories about a line of thunderstorms ahead.