Trump helicopter close call linked to White House work

US investigators said construction at the White House contributed to President Donald Trump's helicopter passing too close to a passenger plane over Washington on August 4.

The National Transportation Safety Board said in a preliminary report that Marine One had taken off from a temporary site on the Ellipse, outside the White House grounds, while a permanent helipad was being built inside the grounds.

The NTSB cited Federal Aviation Administration estimates that the presidential helicopter and an Envoy Air passenger plane were separated by 0.82 miles horizontally and 700 feet vertically. Investigators said that was less than the required minimum separation of 1.5 miles and 500 feet.

The NTSB said it was still working to calculate and confirm the distances and that its investigation was continuing.

Investigators said air traffic controllers at Ronald Reagan Washington National Airport did not receive the first radio transmission signalling Marine One's imminent departure, and that a second attempt was broken and unreadable. The report said there was not adequate line-of-sight for communications between the transmitter and receiver site and the Ellipse.

The White House and the FAA have both said Trump was never in danger.

In January, a collision between a passenger plane approaching the same airport and a US Army Black Hawk helicopter killed 67 people.