A Hawker Hunter jet crashed on to the A27 highway in Shoreham, West Sussex, during an aerial display at the air show on Saturday.
At least 11 people are thought to have died but more bodies are expected to be recovered after the jet's wreckage is removed.
Local authorities began clearing up the debris from the crash site and a crane has been deployed to lift wreckage at the scene, amid fears that several bodies will be found.
Assistant Chief Constable of Sussex Steve Barry said: "The number of highly likely dead remains at 11, but may rise. However, we do not expect that figure to be greater than 20, probably fewer."
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He said there were cyclists and onlookers in the area at the time of the crash.
"It makes it very complicated to establish who was where and who we can actually confirm has been a victim of this crash," he said.
"We are offering every assistance to the Air Accident Investigations Branch as it seeks to establish the circumstances of the crash," it said in a statement.
"At Shoreham we have always taken those safety arrangements very seriously. The team at Shoreham have many years of experience in running air shows throughout the UK and all aircraft have to be certificated and all pilots authorised by the CAA before they are allowed to undertake display routines at any air show," it added.
The pilot of the aircraft Andy Hill, 51, from Sandon, near Buntingford in Hertfordshire, remains in a critical condition in hospital, having been pulled from the burning wreckage.
Aviation regulator Civil Aviation Authority said it was considering whether airshow safety requirements should change.
In a statement, it said: "The safety standards that must be met by all major civil air displays in the UK are among the very highest in the world.
"All air display arrangements, including the pilots and aircraft, must meet rigorous safety requirements. Individual display pilots are only granted approval following a thorough test of their abilities.