Cruise companies Cunard and P&O have lengthened the suspension of operations due to the coronavirus pandemic.
Two of Cunard's three ships began to sail back to Southampton earlier this month when it halted its international holiday voyages.
In a statement, president Simon Palethorpe said it was "prudent" to extend the suspension until 15 May.
Fellow Carnival company P&O Cruises said the maiden voyage of its new ship, Iona, might be delayed.
Passengers from its three ships were flown home when it announced it was ending cruises on 11 March.
Cunard's Queen Victoria arrived back in Southampton from Florida last week and Queen Mary 2 is returning from Australia with passengers who were unable to fly due to medical conditions.
Mr Palethorpe said the pandemic was "without doubt, the most challenging period the travel industry has ever seen".
"It's clear the pace of developments around Covid-19 has increased significantly. We will continue to monitor government guidelines and restrictions and this may mean there are further changes to the timing when each of our ships return to service."
P&O president Paul Ludlow said it was "not feasible" to return to sailing after its initial 30-day pause.
He also said there could be a delay to the arrival of P&O's new ship Iona, which is due to be named in Southampton this summer because restrictions had forced the slowdown of work at the Mayer Werft shipyard in Germany.
Other lines which use Southampton - Princess Cruises, Saga and Fred Olsen - also cancelled voyages when the government advised against cruise ship travel for people aged over 70, and those with pre-existing health conditions.