Boeing has admitted it has to redesign parts of its 787 Dreamliner following claims by one of its biggest customers that the aircraft will suffer fresh delays.

Steven Udvar-Hazy, chairman of aircraft-leasing company International Lease Finance Corporation, said the aircraft would be delayed another six months – putting the first deliveries back until late next year. ILFC has placed a major order for the 787.

The Dreamliner was originally expected to make its maiden flight last year.

In a statement, Boeing said: “We are doing some redesign work. There are a whole load of things going on.”

The manufacturer did not concede production would be delayed again, but said it was undertaking a review.

A fresh delay would affect UK airlines including the merged First Choice Airways and Thomsonfly, Monarch and British Airways.

First Choice Airways planned to be the first UK carrier to fly the 787, which has a carbon-composite body and will be significantly more fuel-efficient than the long-haul aircraft it replaces. But when it ordered the 787, it expected the first in early 2009.

The redesign is believed to involve the parts which hold the wings in place. The 787 has attracted 857 advance orders, more than any other aircraft in history.