Seven people have been confirmed dead after a plane crashed during an airshow in Shoreham-By-Sea.
Police say the plane, believed to be a Hawker Hunter, hit several cars on the A27 in West Sussex at about 1.20pm.
The pilot was not among the deceased but police confirmed he was "critically ill and fighting for his life" at Royal Sussex County Hospital.
Fourteen others were injured and police warned they could yet discover more casualties.
A police spokesman said: "Emergency services have declared a major incident and a number of helicopters have been deployed to the scene to evacuate casualties to hospital.
"South East Coast Ambulance Service have confirmed that there have been seven fatalities declared at the scene, one patient with serious life-threatening injuries has been transported to Royal Sussex County Hospital and a further 14 patients treated for minor injuries.
"The casualties are all believed to have occurred on the road at this time and there are not thought to be any injuries to anyone actually on the airfield.
"West Sussex Fire and Rescue Service has sent 10 appliances to the scene."
The jet ended up in a bush, according to a spokesman for Shoreham Airshow.
Laura Raymond, who was commentating on the display for Splash FM, told Sky News: "There was a ball of fire, we didn't even hear an impact - and then plumes of black smoke. It's being described by the commentator as a tragic incident."
She said about 20,000 people were at the show and they descended into "hushed silence".
The A27 will remain closed until 6am on Monday, Highways England has said.
The show was due to recommence on Sunday but has now been called off.
Prime Minister David Cameron sent his condolences to the victims' families.
A Downing Street spokesman said: "The Prime Minister sends his heartfelt condolences to the families of the people who were so tragically killed after a jet crashed into several vehicles in West Sussex.
"The Prime Minister's thoughts and prayers are with the families and friends of the victims."
The Air Accidents Investigation Branch said: "We will be conducting a civil air accident investigation and a team is on site.
"We are working closely with Sussex police and a report will be produced in due course."
It is the second fatal crash at the Shoreham Airshow in recent years after James Bond stuntman Brian Brown died in September 2007.
The 49-year-old was carrying out an unplanned barrel roll at a re-enactment of the Battle of Britain.
The Hawker Hunter was introduced in the 1950s and retired from military service in 2014.