By John Bowker and Gavin Haycock

LONDON (Reuters) - British Airways (BAY.L: Quote, Profile, Research) said on Friday it would delay moving around 120 flights to the airline's new Terminal 5 at Heathrow in an effort to make sure it can handle the extra passengers and baggage involved.

The airline had planned to switch almost all its long-haul flights from Terminal 4 to Terminal 5 on April 30, but BA Chief Executive Willie Walsh told reporters this had now been put back until at least June 5.

By then, passenger volumes are expected to be lighter at Heathrow, the world's busiest international airport, following the late-May school breaks and a public holiday on May 26.

The delay is the latest move by BA to get Terminal 5 running properly after an unmitigated public relations disaster last month when hundreds of flights were cancelled and tens of thousands of bags went missing in disruption caused by baggage handling problems.

This month, BA said T5 disruption had so far cost it around 16 million pounds ($32 million).

Walsh said media speculation about the extent of the costs had been "way off the mark" and that an update would be given in due course.

ABN analyst Andrew Loddenberg told Reuters he did not expect the latest setback to have an impact on costs.

"The 16 million pounds was principally associated with the cancelled flights. This is a deferral. At the margin there would be economies by operating in one less terminal, but it is not going to be material," he said.