The Nigerian Airspace Management Agency (NAMA) has explained why United Airlines chose to make an air return to Nigeria.

In a statement on Wednesday, Abdullahi Musa, NAMA’s director of public affairs and consumer protection, said the decision to return to Nigeria was made by the pilot based on his assessment of the situation and the perceived safety of landing at the departure airport.

The U.S. National Transportation Safety Board said on Monday it is investigating a United Airlines flight on Friday from Lagos, Nigeria to Washington D.C., in which a sudden aircraft movement led to injuries of passengers and cabin crew.

Six people were taken to hospital, and many more were injured after a United Airlines flight from Lagos heading to Washington D.C. experienced a sudden in-flight movement. The United States has opened a probe into the unexpected movement, as the cause is still unknown.

The authorities in Nigeria said that the United Airlines plane had to return to Lagos after the episode. Six people were treated at a hospital, officials said.

A United Airlines flight was traveling from Lagos to Washington, D.C. when it experienced "sudden aircraft movement."