Tui has extended its summer holiday cancellations into July.
The move will affect trips to Greece, Croatia, Cyprus, Italy, Malta and Spain, among others.
It comes amid speculation the UK government will delay lifting the UK’s remaining Covid restrictions, which could impact international travel.
All holidays to Zante departing up to and on 28 June have been cancelled.
All departures to Aruba, Croatia, Cyprus, Greece, Italy, Jamaica, Malta, Spain and Tui lakes and mountains destinations, meanwhile, have been cancelled up to and on 4 July.
Holidays departing up to and on 11 July to Bulgaria, Cape Verde, Costa Rica, the Dominican Republic, Egypt, Mexico, Morocco, Tunisia and Turkey have also been pulled by Tui.
Additionally, the operator has cancelled holidays including non-Tui flights to Indonedia, the Maldives, Mauritius, Sti Lanka, Tanzania, Thailand and the UAE.
Tui has said all customers will be contacted to inform them of their options, which include moving their holiday to a later date or switching location and receiving a booking incentive, or a refund.