Definition
A leased telecommunications service formerly used within the FAA's National Airspace System to carry administrative and operational data traffic between facilities over circuits leased from commercial carriers, classified as either A (higher priority) or B (lower priority) service.
Plain English
A communication line the FAA rented from a phone company to send messages between its facilities, with two priority levels — A for more urgent traffic and B for routine traffic.
Context Anchor
Seen mainly in FAA acronym lists, NOTAM-related references, and older aviation communications material, rather than as a cockpit term a pilot normally says aloud.
Derivation
‘Leased’ because the FAA did not own the lines — it paid commercial carriers to use them. ‘A’ and ‘B’ simply labeled the two service tiers, with A reserved for higher-priority traffic.
Why Pilots Care
A pilot is most likely to need this term when reading FAA reference material or decoding an aviation abbreviation. It helps identify that the subject is an information-distribution service, not an aircraft system or flight procedure.
Intuition Check
Do not read “leased” as meaning an aircraft lease. Here it means the communication service or line is dedicated for aviation use through an arranged provider service.
Example Sentence 1
The facility's older administrative messages were routed over LABS circuits before the system was modernized.
Example Sentence 2
During the facility upgrade the technicians verified that the new LABS lines carried both voice and radar data without dropouts.