Washington Dulles International Airport (IAD) is at a historic turning point. The U.S. Department of Transportation (DoT) has issued a Request for Information (RFI) to revitalize Washington Dulles International Airport—one of the most ambitious airport redevelopment efforts in the United States. The initiative is not simply about adding infrastructure; it represents an opportunity to rethink how Dulles operates, grows, and serves the region over the coming decades, guided by a long-term vision for capacity, efficiency, and passenger experience.
ALG addresses this challenge with a clear, practical approach that differs from most proposals. Instead of starting with architectural ideas for terminal expansion, we focus first on understanding the airport’s operational reality—how it performs today, where bottlenecks occur, and how passengers and airlines move through the system. This data-driven foundation includes:
- Analysis of traffic flows and long-term demand trends
- Operational diagnostics of concourse and terminal performance
Based on these insights, ALG can propose a redevelopment plan that is ambitious yet realistic, respecting the iconic Saarinen design while addressing structural inefficiencies in Dulles’ legacy layout.
Structural and operational challenges limiting Dulles today
Washington Dulles International Airport (IAD) is an aging airport with decades-old terminals, where inefficient layouts and outdated infrastructure lead to a poor passenger experience and limited capacity.
Dulles’ terminal system was groundbreaking when it was conceived, but its fundamentals now constrain the airport’s competitiveness. The airport relies on a central Processor Building and four main concourses (A, B, C and D). However, over 95% of the gates sit in remote satellite concourses, disconnected from the Main Terminal by long walking paths and mobile lounges.
As a result:
- Walking distances often exceed 10–20 minutes
- Minimum Connecting Times are structurally higher than peer hubs
- Passenger experience across the airport feels fragmented and unintuitive
Although the current Master Plan contemplates new infrastructure, the net increase in contact gates falls far short of the long term traffic requirements, especially given United’s and Star Alliance’s continued expansion. Meanwhile, the Main Terminal’s processing systems—check in, security, baggage claim—have not grown proportionally with O/D demand, creating persistent congestion during peak hours.
Traffic evolution: an airport serving two very different demand profiles
A- United + Star Alliance: the core of the hub system
United Airlines and Star Alliance partners account for the majority of IAD traffic. In 2024, they transported 20.0 million passengers, representing a 50% increase since 2015, with a traffic mix of 59.7% O/D and 40.3% connecting.
This connecting share—large for a U.S. hub—demands:
- predictable, short walking paths
- high contact gate availability
- efficient banked operations
- minimized remote stand activity
Dulles’ current layout struggles to meet these requirements.
B- Other carriers: a predominantly O/D segment with rising expectations
Other airlines at IAD represent 7.3 million passengers in 2024, about 27% of the airport, with a 98.5% O/D profile.
These passengers rely heavily on:
- Main Terminal processing capacity
- curb to gate efficiency
- ground transportation connectivity
Yet the Main Terminal consistently reaches saturation during peak hours—a structural limitation for future growth.
Operational banks and movements: peak intensity meets outdated infrastructure
IAD operates as a highly banked hub for United and Star Alliance. Bank structures generate intense peaks that strain the existing concourse and gate system. According to operational analysis:
- Peak arrivals reach ~89 ATMs/hour
- Peak departures reach ~88 ATMs/hour
- Total movements peak at 95–100 ATMs/hour around 16:00
These peaks lead to:
- gate conflicts
- bottlenecks in passenger flows
- higher risks of missed connections
- increased reliance on remote stands
The rigid geometry and segregation of concourses amplify these challenges, reducing operational resilience.
Gate capacity constraints: the central bottleneck for future growth
Today, gate capacity at IAD is highly constrained, particularly in the afternoon bank, limiting additional flights and threatening traffic growth and hub‑and‑spoke efficiency.
Gate supply and allocation patterns across concourses reveal a system operating at or near capacity:
- Concourse C/D + Z: 50 gates
- Concourse A/B: 44 gates
- Regional concourse: 50 gates
Across multiple representative days in 2025, peak-hour gate occupancy consistently nears full capacity, particularly in Concourses C/D and Z, operated by United Airlines, with all 50 gates in simultaneous use.
Operational implications include:
- Inability to add flights at commercially optimal times
- Limited growth potential for long-haul markets
- Reduced resilience for irregular operations
- Constraints on bank optimization
This bottleneck is one of the strongest inhibitors of IAD’s competitiveness as a growing hub.
ALG’s vision for a future-ready IAD
ALG’s vision delivers a future-ready Dulles, resolving the core structural and pax experience constraints through scalable gate capacity, walkable terminals, efficient operations, and an expanded Main Terminal ready for long-term growth.
1. Restoring walkability as the foundation of the passenger experience
Dulles’ long walking distances and fragmented concourse system are among its most limiting features. With over 95% of gates located in remote satellites, the airport’s geometry inherently reduces transfer efficiency and increases MCTs.
ALG’s redesign restores walkability as the central organizing principle. New concourses are directly connected to the Processor Building, eliminating reliance on mobile lounges and reducing transfer times by several minutes across most itineraries. Straightforward pedestrian circulation—reinforced with intuitive wayfinding and visual transparency—creates a passenger journey that rivals modern benchmark hubs globally.
To support short connections and enhance resilience, ALG proposes a fast, elevated airside people-mover, not as a replacement for walking, but as a complement for time-critical flows during peak banking periods.
2. A scalable gate development strategy aligned with long-term traffic growth
The gate system’s structural inflexibility is a direct threat to IAD’s future. Peak-hour usage regularly reaches the limit of available concourse capacity, especially during the afternoon bank when the airport processes 95–100 ATMs/hour.
ALG proposes a phased, scalable gate strategy that evolves with demand:
- Phase I: Increase from ~130 to ~140 gates, prioritizing walkable concourses.
- Phase II: Expand to 180–200 gates, enabling growth toward 45M passengers by 2045 and scalability to 75M in the long term.
- Phase III: Transition older concourses (like C/D) from passenger facilities to operational support.
This approach ensures that IAD can grow sustainably, accommodate new long-haul services, and attract global carriers who require guaranteed contact gate availability.
3. Strategic repurposing of concourse C/D to preserve resilience during transformation
Concourse C/D, though operationally obsolete, still plays a critical role in providing gate and stand capacity. Demolishing it prematurely would disrupt operations during a period of peak demand.
ALG therefore recommends a staged repurposing in which C/D is:
- decommissioned for passenger use
- retained as an operational buffer, including: overnight aircraft parking, remote stands, maintenance positions, irregular operations mitigation, and bank overflow relief
This strategy preserves essential flexibility during redevelopment and prevents gate constraints—already acute—from worsening.
Once new walkable concourses are delivered, C/D can transition to long-term operational roles or selective retirement.
4. Expanding main terminal capacity while preserving Saarinen’s architectural legacy
ALG’s proposal respects the iconic Saarinen terminal while addressing the growing pressure on its processing systems. O/D traffic—particularly from non-United carriers, whose traffic is 98.5% O/D—has increased significantly.
To support this growth, ALG proposes targeted expansions within the existing parking footprint, enabling enhancements such as:
- expanded check-in hall capacity
- redesigned security screening areas
- increased baggage claim throughput
- more efficient arrivals circulation
- improved curbside and roadway access
These improvements preserve the architectural character of the structure while ensuring that the Main Terminal can support traffic growth to ~45M passengers in Phase I, and well beyond in future phases.
A strategic investment in the future of the Washington region
With an anticipated program scale exceeding $10 billion, Revitalizing IAD has the transformative power of landmark airport redevelopments such as JFK’s Terminal One. The project strengthens:
- regional competitiveness
- global connectivity
- economic development
- IAD’s role as the international gateway to the U.S. capital
Conclusion: defining the Dulles of the future
ALG believes the future IAD must be defined by three core principles:
- A seamless, intuitive, and fully walkable passenger experience
- A resilient operational model that supports both O/D and connecting flows
- A scalable, data-driven development framework that honors architectural heritage
By resolving today’s constraints and preparing for tomorrow’s demands, Dulles can evolve into a world-class global hub, aligned with the ambitions of the Washington metropolitan region for decades to come.
About the authors
Xabier Iglesias
Aeronautical Engineer with an Executive MBA from IESE Business School and over a decade of international experience advising airport operators, investors and public institutions. Specialized in airport strategy, PPP structuring, traffic forecasting, financial modelling and technical due diligence for complex brownfield and greenfield projects. Experienced in leading multi‑stakeholder engagements involving master planning, concession design, operational transitions, and infrastructure development. Senior Manager at ALG.
