According to a BBC report, the majority of the 38 people killed in the attack on a Tunisian beach resort were British, the country’s prime minister Habib Essid has said.
Islamic State extremists have claimed responsibility for the attack.
At least five Britons have been confirmed dead by the Foreign Office, which warned the death toll could rise.
Thomson and First Choice said their customers were among “a number of fatalities”, and they had sent 10 planes to bring home 2,500 tourists.
The first began to arrive back in the UK on Saturday morning.
Tunisians, Britons, Germans, Belgians, French and at least one Irish citizen were among those killed when a gunman opened fire on tourists. Thirty-six others were wounded.
The “majority” of the dead were British, Mr Essid said in a press conference, hours after Defence Secretary Philip Hammond said a “high proportion” of casualties would have been British.
None of the Britons’ identities have been released, but Irish national Lorna Carty, who was in her 50s, was confirmed dead by the Irish government.
A gunman was shot dead by police.
Jeremy Moore, who landed at Gatwick on Saturday, said he was “pleased to get home”. He also said passengers on his plane were clapping and cheering as it took off and landed.