More than half of the airworthy Second World War-era planes flown by the Royal Air Force (RAF) have been grounded over engine-related safety fears.
Aircraft operated by the RAF's Battle of Britain Memorial Flight (BBMF) were scheduled to fly at the Biggin Hill Festival of Flight, near Bromley in south-east London, and the Eastbourne International Airshow in East Sussex.
But BBMF's Lancaster bomber, four Spitfires and two Hurricanes will not fly until they have been checked after a fault was found with the engine of one of the Hurricanes.
A public display at the Weymouth Carnival on Wednesday was cancelled after the fault was discovered and Thursday's performance in Eastbourne has also been pulled.
An RAF spokesman said the fault with the Merlin engine was still being investigated and it was unclear how long the planes would be grounded.
The spokesman said: "A routine inspection has highlighted a fault with one of the Merlin engines in a Hurricane aircraft.
"We are currently investigating the fault and, as a precaution, flying of Merlin engine powered aircraft has been paused.
"We are still operating Griffon powered aircraft, including Spitfires and Chipmunks.
"We realise the disappointment this will be to many supporters and airshow organisers, however safety is our paramount concern."
Based at RAF Coningsby in Lincolnshire, the BBMF keeps six Spitfires, two Hurricane Mk 2Cs, a Lancaster, a C47 Dakota and two Chipmunks preserved in airworthy condition.
They are some of the last Second World War planes to still fly today.
Andy Patsalides, marketing manager for Biggin Hill Airport, said the BBMF were a "crowd-pleaser" and it was disappointing the squadron, which was formed at the airport 60 years ago, might not be there to celebrate the airport's centenary.
He said: "The crowds will be a bit disappointed - everyone has got a soft spot for BBMF. They've been been very, very good to us because it's their spiritual home.
"The crowds will be a bit disappointed but in our business it's safety first."
Phil Evans, director of tourism and enterprise for Eastbourne Borough Council, said "The Battle of Britain Memorial Flight has been cancelled for today at Eastbourne Airshow following news of an engine issue.
"Airbourne is still expecting a packed programme of displays today, and we are looking at alternatives, should the Battle of Britain Memorial Flight continue to be grounded over the remainder of the four-day show."
The Hurricanes, along with Spitfires and the Dakota, were scheduled to fly at the Whitby Regatta, in Yorkshire, on Saturday and Sunday and Ian Winspear, voluntary secretary of the organising committee, said he had yet to hear if the flypast had been cancelled.
"It would be a big disappointment to us if they did not come," he said.
"There are people who are coming specifically to see them."
He said they had applied for the RAF Red Arrows but had been offered BBMF as a "sweetener". He added it would not be a "disaster" for the event if their display was cancelled.