Hundreds of flights cancelled as US shutdown grinds on

The longest shutdown in US history became even more severe today as hundreds of flights were cancelled by the federal government to reduce strain on air traffic controllers, who haven't been paid for five weeks. We hear from travellers, airport staff and a Republican congressman on the growing political pressure to find a deal in Congress that would end the government shutdown.

Also on the programme: one of the pioneers of artificial intelligence tells us why he's profoundly concerned about the potential harm from the technology. And the geneticist who co-discovered DNA, James Watson, has died aged 97. We hear from a lifelong friend.