The airport is said to be considering a new terminal just to the west of T5, where British Airways is based, with space for another 25 million passengers a year as part of plans for a third runway.
Original plans for the new runway, to the north west of the airport, had included a full-size T6, but concerns about costs and the difficulties of building an underground road system to service it have meant a rethink, according to the paper.
Heathrow is anxious to keep costs down to avoid a row with airlines, which will have to pass them on to passengers. The final blueprint will be subject to a vote in parliament before next summer, with planning battles likely to rage on into the 2020s.
