On March 20, 2025, some important changes are coming to the North Atlantic High-Level Airspace (NAT HLA). While they may not impact most of the flights you see on Flightradar24, they mark a significant shift in how certain aircraft can navigate across the Atlantic.
To understand the impact, let’s start with a quick refresher on what the NAT HLA is and how traffic moves across it.
The NAT HLA: A Unique and Complex Airspace
The NAT HLA spans FL285 to FL420 over the North Atlantic, connecting Europe and North America. Traffic in this airspace follows predictable patterns, largely dictated by the powerful jet streams:
- Eastbound peak: 00:00–09:30 UTC (taking advantage of tailwinds).
- Westbound peak: Later in the day, when the return flow picks up.
Aircraft typically follow the Organized Track System (OTS) or random routes aligned with these winds, maximizing efficiency and minimizing fuel burn.
Because of no radar or continuous VHF coverage (except in limited areas), aircraft separation is carefully managed:
- Vertical: 1,000 feet.
- Lateral: 1-degree latitude (approx. 60nm), with some half-track (30nm) options.
- Longitudinal: 10-minute spacing.
Given these constraints, strict equipment requirements apply for entry into the NAT HLA.
What Equipment Is Required?
To operate in the NAT HLA, aircraft must meet performance and equipage standards, including:
Navigation Requirements
Aircraft must be capable of maintaining accurate navigation through at least two independent Long-Range Navigation Systems (LRNS), which can be:
- Inertial Navigation System (INS)
- Global Navigation Satellite System (GNSS)
- IRS-based navigation system
Communication Requirements
Aircraft must carry two independent Long-Range Communication Systems (LRCS), including:
- At least one HF radio
- The second system can be HF, SATVOICE, or CPDLC
Surveillance Requirements
- ADS-C and CPDLC (Controller-Pilot Datalink Communication)
- ADS-B, which allows limited ATC surveillance coverage
Without meeting these requirements, aircraft cannot operate in NAT HLA airspace. However, there has been one exception: the Blue Spruce Routes.
The Blue Spruce Routes allowed aircraft with only one operational LRNS to cross the North Atlantic, provided they followed specific, more northerly routes that passed near Iceland and Greenland. These routes relied on ground-based navigation aids (VORs and NDBs) and had some limited VHF coverage.
These routes got their name from WWII-era military flights—propeller aircraft (often made of spruce) had blue-painted propeller tips, which helped make them less visible in the air while still preventing personnel from walking into them on the ground.
What’s Changing on March 20, 2025?
When the new NAT Doc 007 (the ICAO governing document for NAT HLA operations) takes effect, the Blue Spruce Routes will be eliminated. The Blue Spruce Routes are being removed because the ground-based NDBs and VORs that supported these routes are being decommissioned. There are no longer enough functioning aids to ensure safe navigation on these routes.
Not all reduced-equipage routes are disappearing. The Tango Routes and certain corridors over Spain, the Azores, and Greenland will remain available.
Aircraft without two functional LRNS will no longer be able to use the former Blue Spruce Routes to cross the NAT HLA. Instead, they will have to:
- Fly above FL420 (unlikely for most aircraft).
- Descend below FL285 (which significantly increases fuel burn).
- Re-route around the NAT HLA entirely (again significantly increases fuel burn).
Spotting This on Flightradar24
If you notice an aircraft approaching the NAT HLA boundary and then descending below FL285, this could indicate that the aircraft lacks sufficient navigation systems, has experienced a navigation system failure and had to re-clear with ATC, or it is adjusting for fuel planning before continuing.
A more dramatic descent below FL285, followed by a course change toward land, could indicate a fuel stop or diversion for repairs.
Weather Deviations and Emergencies
If an aircraft encounters weather and needs to deviate more than 5nm from its track, but can’t contact ATC, it follows a contingency procedure:
- Turn 30° off track.
- Climb or descend 300 feet (to avoid conflicts).
On FlightRadar24, if you see an aircraft turning 30° off track and shifting 300 feet vertically, this is likely a weather deviation.
If instead, you see an aircraft descending below FL285 and offset by 500 feet, this likely indicates a serious in-flight emergency—in which case, the aircraft should also be squawking 7700.
What this all means for NAT HLA operations
From March 20, 2025, aircraft lacking two operational LRNS will no longer have an exception allowing them to cross the North Atlantic at high altitude.
For operators, this means:
- Ensuring all transatlantic flights meet full NAT HLA equipage requirements.
- Avoiding last-minute surprises by confirming system redundancy before departure.
- Factoring in potential fuel stops if a navigation system degrades mid-flight.
While most airspace users won’t feel a direct impact, this change simplifies NAT HLA operations and ensures a consistent, modernized standard for transatlantic flights.
