Terrorists on witness protection were able to travel on flights because their new identities were not updated on the US no-fly list, a watchdog has found.

The US justice department report said its Witness Security Programme had failed to give the new names to the FBI-managed Terrorist Screening Centre.

The miscommunication allowed a “small but significant number” of suspected or known terrorists to board aircraft.

As a result of the security gap “it was possible for known or suspected terrorists to fly on commercial airplanes in or over the United States and evade one of the government’s primary means of identifying and tracking terrorists’ movements and actions”.

The justice department said it had now amended its information sharing, the BBC reported.

A restrictive travel policy had since been fully implemented, it added.

Terrorism-linked witnesses have long been eligible for federal protection, allowing them to be provided with new identities and resettled.

The programme has shielded those who co-operated in prosecutions for the 1993 World Trade Center bombing, the 1995 bombing in Oklahoma City and the 2009 New York City subway suicide-bomb plot.