TOUR operator P&O Cruises was sailing along on calm seas yesterday after reporting a buoyant trading period for last year.

The company said that all ships in its cruises division were sailing at full capacity and that strong demand was continuing into 1999.

P&O operates two divisions - Princess Cruises in the US and P&O Cruises sailing out of Southampton - shipping almost six million passengers last year.

Princess Cruises operates nine ships, led by the summer launch of the 109,000-ton Grand Princess last year - the largest cruise ship in the world offering 2600 berths.

The introduction of the Grand Princess had led to a 23% increase in capacity but the percentage of cabins booked was still slightly up on the same period last year.

While this led to a ''significant improvement in productivity yield'' overheads were continuing to come down with the introduction of the new ships, said P&O.

Seven-day cruises were proving much more popular than the longer-haul cruise destinations.

The UK division operates three ships, the Star Princess, Arcadia and Victoria. Even though the Canberra was withdrawn from service towards the end of last year and the Victoria had an extended refit, capacity increased by 9% last year compared to 1997.

The 1999 booked revenue and yields were comparable to the same position as last year, the company said.

Strong demand overall was led by the over-50s' passengers, described as the ''post-war baby boomers'', which led to fully booked cabins.

The cruise division is one of the largest areas in P&O's diversified business, accounting for a quarter of its total assets.

It is one of the three-largest cruise ship businesses in the world, along with the US-based Carnival and Royal Caribbean companies.