A Ryanair flight from London Stansted to Porto is currently priced at £232.99 on 17 May, while anyone travelling the day before would pay only £14.99.
The UK travel firm Not Just Travel, which employs 800 people, has recorded a 50% increase in summer bookings in the last seven days.
The travel firm is recording more bookings than usual to Portugal and Malta, which are expected to be on the UK’s green list of quarantine-free travel.
Thomas Cook said Greece, the Canary islands and the Balearic islands were also popular summer destinations this year, even though they are expected initially to be put on the UK’s amber list, which will require a 10-day quarantine on the return home and two PCR tests.
While flight prices are going up, hotels are cheaper than usual because there are so many unfilled hotel rooms, Child said.
Emma Coulthurst, of the holiday price comparison site TravelSupermarket, said there were package holiday bargains available for under £300 per person, for example a week in a three-star hotel on the Algarve in August for a family of four from £253 per person.