Operators and airlines have reset to 17 May as the start date for the summer season.
Departures before this date have been cancelled by Tui UK and Jet2, with Covid refund and cancellation policies applying.
Andrew Flintham, Tui UK and Ireland managing director, said: “In line with the UK government’s latest lockdown announcement, all Tui holidays from England will not operate before 17 May.
“We will be contacting impacted customers directly, in departure date order, to discuss their options, which will include amending to a later date with an incentive or cancelling and receiving a full refund.
“We know our customers are looking forward to their holidays, so to offer continued flexibility and reassurance, we have extended our free changes policy to the end of June. Those due to travel between 17 May and the end of June can change their booking to a later date fee-free.”
Jet2.com and Jet2holidays have also extended the suspension of all flights and holidays until 17 May.
Jet2 said: “Where customers yet to travel are affected by any programme changes, Jet2holidays will automatically cancel their booking with a relevant refund, and their team of travel experts will be in touch to help them to book their summer getaway for later in the year.”
EasyJet will continue to operate some flights during lockdown, although leisure travel remains illegal until at least 17 May.
EasyJet chief executive Johan Lundgren said: “Our Protection Promise means that customers can book with confidence knowing that if they are unable to travel or their plans change so can their flights or holiday, and we’ve put more flights and holidays on sale this summer to even more destinations, so that customers have more choice to book something to look forward to.”