Plain English Meaning
Jet airways are the high-altitude highways in the sky that airliners and other high-flying aircraft use. They start at 18,000 feet and go up to about 45,000 feet, and each one has a name like J80 or J146.
Full Definition
Published high-altitude airways in the United States that extend from 18,000 feet MSL up to and including flight level 450 (FL450). They are identified by the letter J followed by a number (for example, J80) and are based on VOR navigation aids. Aircraft flying jet airways operate in Class A airspace under instrument flight rules.
Context Anchor
Seen on high-altitude en route charts and in route clearances such as “cleared via J80.”