Question: On an airline flight from New York to St. Thomas, I noticed that we ventured 400 miles offshore. Who controls this airspace, presumably beyond VHF and radar range?
Answer: Most traffic between the Northeastern U.S. and the eastern Caribbean uses this routing, several hundred miles shorter than following the East Coast. The airspace is called the Western Atlantic Route System, known by its acronym, WATRS. It uses 12 published airways labeled (from west to east) L451 through L462. Most are oriented north-south and spaced 60 nm apart. The availability of Bermuda as an engine-out alternative makes these routes usable even for non-ETOPS aircraft.
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WATRS is controlled by New York Oceanic FIR, which owns a huge swath of the western Atlantic between 21 and 45 degrees north. The small portions of WATRS that are within radar and VHF coverage operate similarly to domestic airspace. Elsewhere, nonradar position reporting procedures apply via high-frequency (HF) radio on 3,000 to 22,000 KHz. HF is not subject to the line-of-sight limitations of VHF because it bounces signals off various layers of the ionosphere. Signal propagation varies, with usable frequencies changing with sun angle and transmission distance—and interference from solar storms.
When propagation is poor, the few marginally usable frequencies become congested. You are not speaking directly to ATC but communication specialists at ARINC who relay your position reports and requests to the controllers. All this means that weather deviations must be requested well in advance, and emergency contingency procedures envision the likelihood of delayed communications. In recent years, the increased use of controller-pilot data link communications (CPDLC) with satellite communication (SatCom) has eased the com difficulties in WATRS airspace. CPDLC provides automatic position reporting and instantaneous text communication with ATC.
This article first appeared in the July 2023/Issue 939 print edition of FLYING.
