Trump's "triumphal arch" will need to have red lights on top of it after a review of its design alarmed a federal agency, according to reporting by the New York Times.
The 259-foot-tall arch will be less than a mile from the Ronald Reagan National Airport in Washington, D.C., leading the Federal Aviation Administration to recommend red, blinking lights to be added on top, the Times reported.
The FAA identified the arch as an "obstruction," but noted it would have "no significant adverse effect on airspace" in a feasibility study released on Friday, ahead of a formal evaluation, according to the Times.
However, aviation experts are divided over whether the arch would complicate D.C.'s already congested airspace, especially after last year's collision between a commercial jet and an Army Black Hawk helicopter that killed 67 people midair, according to the Times.
The Times' own analysis found that the top of the arch would "jut into an area that is supposed to ideally remain clear for flights."