Updated 2 hours ago The centerpiece of Amazon's HQ2 project in Arlington County might not fly with the FAA. The Metropolitan Washington Airports Authority (MWAA) says the proposed height for the head-turning Helix building is about 13 feet taller than FAA regulations allow that close to Washington Reagan National Airport. Download our NBC Washington app for iOS or Android to get alerts for local breaking news and weather. The plans for the next phase of Amazon's HQ2 include four buildings, providing 2.8 million square feet of office space, spread across 2.5 acres. The PenPlace location, as it's called, is a massive proposal. The Helix is intended to be HQ2's centerpiece, designed to be the tallest, most eye-catching structure to reshape Arlington's skyline.