VDL works. Now we need to act on that evidence

Very High Frequency DataLink (VDL) is not legacy. It is the backbone of aviation and a proven technology that increases airspace capacity today.

The 2025 operational evidence is clear: VDL is reliable, scalable, and already handling the complexity of today’s traffic. The real constraint is not technical limitation, but a persistent narrative that frames it as aging and near its limits.

“VDL is not yesterday’s technology. It is the infrastructure that keeps aircraft flying today and will keep them flying well into the 2030s.”

That is the message Pablo De la Viuda, Head of ATC SITA, wants the ANSP community to hear clearly.

What 2025 proved: VDL is not the bottleneck

For years, industry discussions have been shaped by a single word: crunch. This is the idea that VDL is inherently limited, overburdened, or nearing the end of its usefulness. The term took root more than a decade ago and has lingered stubbornly, resurfacing at conferences and technical debates.

In 2024, a high-profile service interruption, later traced to an external issue, shook confidence across Europe. What followed is the part few people talk about: a full-scale effort by SITA's engineering, operational, and performance teams to rebuild the service, modernize parts of the network, and remove hidden vulnerabilities.

The result? Summer 2025 became the year that rewrote that story:

• No major outages.
• No sustained performance degradation.
• Growing message volumes.
• Increasing Controller-Pilot Data Link Communications (CPDLC) use.
• A network consistently delivering above the level required for real-world operations

For ANSPs who lived through the uncertainty of 2024, this reset the question. VDL's reliability is no longer the issue. What the community does with that reliability now is.

“People often ask whether VDL can handle the future,” Pablo says. “My answer is simple: it’s already handling the present.”

VDL’s “limitations” are misunderstood, not structural

The legacy label brings a common misconception: that VDL is inherently limited and nearing the end of its useful life. But Pablo’s take is different:

“The truth is far quieter and far more compelling. Legacy is about age. But aviation doesn’t retire technologies because of age. It retires them when they stop delivering operational value. And VDL delivers enormous value.”

Almost every commercial aircraft flying today is equipped for VDL. ANSPs globally use it as the primary datalink medium. And every year the infrastructure is renewed: radios, stations, servers, frequencies, monitoring systems, and software are upgraded.

"It's like rebuilding a ship plank by plank. At some point, none of the original wood remains. But the ship is still the ship, only stronger."

Another misconception comes from comparing real-world performance to an ideal standard. A common KPI is 99.9% of message transactions delivered within a set time. It looks simple on paper, but it does not reflect operational reality.

Airspace is not a uniform test environment. Aircraft have different avionics, some modern, some aging. Airspaces vary dramatically, from large Flight Information Regions (FIRs) to small ten-minute corridors. Each handoff generates new messages. Each equipment variation introduces timing differences. And VDL, unlike many systems, is measured end-to-end, including aircraft performance.

“If even one aircraft has outdated or poorly configured avionics, the whole chain feels it,” Pablo says. “But the network still works. Safely. Reliably. Every day.”

Most ANSPs understand this gap. They have lived through peak summers and see that a performance KPI is never the full picture of operational reality.

“As one ANSP told us,” Pablo recalls, “‘I don’t need theoretical perfection. I need predictability.’ And VDL delivers that.”

Airspace capacity depends on VDL

There is a fundamental truth that rarely makes headlines but underpins every conversation about airspace. As Pablo puts it plainly:

“CPDLC is the only technology today that increases airspace capacity. And CPDLC runs on VDL.”

This is not theoretical. Across Central Europe last summer, several CPDLC outages unrelated to VDL consistently forced around 20% of traffic to be rerouted during peak months.

“That’s the scale we’re talking about,” Pablo says. “In some parts of Europe, if VDL disappeared tomorrow, one in five aircraft would have to land.”

That is not a technical incident. It is an airspace capacity event, and it belongs in continuity planning, not just technical review cycles.

“People don’t realize how much airspace capacity depends on datalink,” he says. “But the operational reality is clear. Without it, the skies slow down.”

VDL Untapped — the capacity that hasn’t been activated yet

Inside SITA, a quiet internal project carries a surprisingly bold name: VDL Untapped.

“In the last two years,” Pablo says,“we have deployed a ‘’third alternate frequency’  across Europe. We have new optimization levers. New radio technologies. New architectural possibilities. And more on the way.” 

VDL's supposed limitations are not inevitabilities. They are simply areas of capacity not yet activated.

“We’re discovering capacity, not wishing for it,” he says. “And when we find it, we deploy it.”

SITA is preparing to publish the VDL Untapped roadmap ahead of Airspace World 2026, a clear, evidence-based view of planned frequency expansions, optimization initiatives, and capacity enhancements for the coming years. For ANSPs finalizing capacity plans for the late 2020s, it is the document to request before those plans are locked.

“It’s pure engineering,” Pablo says. “And we want everyone to see it.”

The multi‑link future needs VDL at its core

Satellite-based systems will play an important role. But they extend the architecture; they do not replace the foundation.

“New technologies always inspire excitement,” Pablo says. “But the transition is slow. Adoption takes years. Certification takes longer. Right now, only a tiny portion of the fleet can use these emerging systems.”

No region can move its airspace on the basis of aircraft that do not yet exist. Ground-based infrastructure can be controlled, secured, repaired, and governed locally. Satellites, even European ones, sit beyond that sphere of control.

“When a VDL station goes down, we send someone to fix it the same day,” Pablo says. “When a satellite goes down, you wait. And the network waits.”

That is simply operational reality.

“In the future, datalink will be multi‑link,” he says. “But multi‑link only works if the primary link is stable, sovereign, and universal. That link is VDL.”

What ANSPs should do now

As the regulatory landscape continues to evolve, with new requirements for Communication Service Providers (CSPs), increasing demands around certification, governance, and oversight, Pablo is direct about SITA's commitment:

"We’ve spent the last year aligning with this future. We've committed to the new regulatory framework. We're progressing on certification. And we're ready to adapt to new models of governance that give confidence."

Above all, he emphasizes transparency, one of the most consistent requests from ANSPs.

“They want to know what we’re doing, why we’re doing it, and how we’re preparing for the next decade,” he says. “And that’s exactly what we’re giving them.”

For ANSPs, the immediate steps are straightforward:

• Request the VDL Untapped roadmap before finalizing late-2020s capacity plans.
• Review whether your performance KPI process captures predictability, not just threshold compliance.
• Sequence your multi-link transition plan against realistic timelines for aircraft equipment installation, not optimistic ones.
• Use the 2025 operational evidence in internal conversations where the legacy or crunch narrative is blocking investment decisions.

Looking back from 2036

As the conversation winds down, one final question remains: ten years from now, what do you hope people will say about this period?

Pablo pauses:

“I hope they will say this was the moment the whole community, ANSPs, industry, and CSPs, recognized the true importance of datalink. I hope they say we chose to strengthen the infrastructure that keeps airspace flying. And I hope they say we made the right investments at the right time.”

Then he adds:

“And I hope they’ll say we never let an old narrative stand in the way of new realities. VDL is not something we inherited. It is something we rebuild constantly. It is something we improve constantly. It is something we will keep making stronger.”

As Europe prepares for Airspace World, the question is no longer whether VDL can support airspace.

The question is whether we will invest in it accordingly. 


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