Thomson and First Choice have extended the cancellation of all outbound flights to Tunisia until March 22, 2016.
A spokesperson said customers with holidays booked during the cancelled period will be able to change their holidays to any other destinations without incurring an amendment fee or receive a full refund instead.
The news comes following the terrorist attack on a beach and hotel near Sousse in June, which saw 33 of the Tui Group’s customers killed, 30 of whom were from the UK.
The group has estimated the cost of running under-occupied hotels in the country as up to €40 million, including €10 million repatriation costs in the immediate aftermath of the attack.
Thomas Cook announced earlier this month that it was planning to resume its Tunisia programme on February 14, 2016.