TUI will be spending up to £5 million on new ship Thomson Dream after it takes delivery of the vessel in April next year.
TUI director of cruise David Selby said there will be 10 days after Thomson takes delivery of the ship for any immediate changes, to be followed by a six-week dry-dock in November 2010, by which time they will have been able to see what else needs to be done.
He said: "I want to see how the ship works for our passengers before we make any decisions. The first two cruises will be very important so I will be on board during that time."
Selby was speaking during a three-night mini-cruise for agents last week so they could see the ship, currently sailing as Costa Cruises' Costa Europa, before TUI takes delivery.
Thomson is taking the ship on a 10-year charter with the option to buy it after five years.
Selby said key changes he had identified during the cruise, which was his first chance to be on board while it was sailing, were the sound and lighting in the theatre and the over-bright lights in the dining room. He will also be looking at whether to relocate the kids and teens areas and reckons the large casino area would be better used for extra cabins.
He said: "It is mostly tweaks. What we like about this ship is the feeling of space in the public rooms and we will keep that."
Selby said Thomson Dream, plus the addition of Island Cruises' one ship, Island Escape, to the TUI stable, meant the group would be growing 40% in two years, with capacity for 280,000 passengers in 2010.
Island Cruises was a joint venture between First Choice and Royal Caribbean Cruises, but became wholly owned by TUI in October 2008, after the group, which had already merged with First Choice, bought out Royal Caribbean's 50% stake in the budget cruise line.
Selby said TUI will be spending some £4 million upgrading Island Escape over the next 13 months.