Looking down on Heathrow Airport from its 87-meter-high (285-ft.) air traffic control tower, the challenges that face the world's busiest two-runway airport suddenly become very clear.

With an aircraft landing or taking off approximately every 2 min., runway and parking-stand capacity is at a premium, and the site offers little room for expansion. On every side, the airport is hemmed in by development, which has a dramatic effect on airport efficiency. A single day of inclement weather can bring about a domino effect on operations resulting in hundreds of canceled flights, leaving passengers stranded and the airport's reputation in tatters. No wonder managers are considering moving operations to another site.

Heathrow Airport Holdings has been quietly exploring options for future airport configurations and two new locations never previously examined for the siting of a major new airport. Aviation Week has seen the Heathrow 2025: Masterplan Options & Indicative Layouts documents produced by the Mott MacDonald consultancy that propose 10 options, ranging from a reconfiguration of the current airfield with two runways and new a terminal layout to an entirely new four-runway facility built on greenfield land at one of two locations in the nearby counties of Berkshire and Buckinghamshire to supplement, or more likely replace Heathrow.

The two new sites suggested by the consultants would feature a four-runway layout, not unlike the configuration of Madrid's Barajas Airport (see map). Two runways would be located on either side of a main terminal core, while the other two runways, parallel to the first two, would be slightly offset but more than 1 km (0.6 mi.) apart allowing parallel landing and takeoff operations. The newly built facilities could potentially handle 140 million passengers and 800,000 air traffic movements a year, just under twice Heathrow's capacity today.

One site suggested is at White Waltham, a small general aviation airfield about 15 mi. west of Heathrow and close to the town of Maidenhead. The other is Haddenham, the location of a old World War II glider airfield about 15 mi. from the city of Oxford but more than 30 mi. from the center of London. Local parish councillors contacted by Aviation Week were taken aback by the suggestion that the countryside near their homes could be turned into a major international airport.

The Haddenham site would perhaps be the most controversial, as the layout suggests the virtual removal of two villages, Chearsley and Long Crendon. Both sites are in open countryside, however, and have the advantage of being close to major transport links. White Waltham, would be built almost on top of the M4 motorway and is close to major rail links, while the Haddenham location is close to the M40 motorway and within a few miles of the government's planned but controversial High Speed 2 (HS2) rail route to Birmingham, a move that would boost transport times into Central London.

Heathrow Airport officials tell Aviation Week the documents are early drafts developed by consultants last year. “They are not designs that have been endorsed by Heathrow Airport,” the officials say. “Heathrow will be making its considered submission to the Airports Commission in July.”

A new facility to replace Heathrow is a highly unlikely scenario, so the focus is likely to be back on the current airport's ability to retain its position as the U.K.'s main hub into the future.

Politicians regularly highlight the failures of Heathrow and its ability to stay open in the face of snow or fog, but they are considerably more reticent about helping to fix it. The building of new runway capacity in the southeast of England is seen as a political “hot potato” and ministers have been reluctant to make a decision which could bring extra noise to hundreds of thousands of city dwellers. And if a third Heathrow runway is unpopular, politicians are going to be even more reluctant to approve the building of a new airport, even if its creation could deliver a long-lasting economic legacy to the region.

Since the coalition government came to power in 2010 and withdrew support for another runway at Heathrow—reversing a 2009 decision made by the previous Labour administration—no fewer than seven new airport options have been suggested. Six of them would lie east of the city, using reclaimed land in the Thames Estuary. One of those, suggested by London Mayor Boris Johnson, was enthusiastically dubbed “Boris Island.”

But many believe an airport in the Thames Estuary is the wrong location for a London airport, since it would be difficult to reach for many people. Indeed, a key part of Heathrow's success has been its location to the west of London, and its proximity to the M4 corridor, where some of the world's largest multinational companies are headquartered.

The Heathrow 2025 masterplan also highlights a range of options for change at Heathrow, including two configurations for a third runway to the north of the airport. One features a short runway, to be primarily used for short-haul and domestic flights, combined with a new terminal in between the new runway and the current northern runway. The other suggests a third longer runway and another set of satellite terminals in the northeast corner of the airport.

Three options for four runways on the Heathrow site are also suggested. One proposes building a new fourth runway to the south of the current southern runway, construction of which would require demolition of the airport's current cargo facilities. Another alternative would see the runway moved toward the east, necessitating the demolition of both the freight areas and Terminal 4. And the third option, which has made it into the national press, would essentially rebuild Heathrow with four runways on land just west of the current airport, a move that could also reduce the number of people effected by noise, at least in London.

Heathrow air traffic has been affected by the economic downturn, dwindling since its peak in 2008, but it is forecast to rebound by 2018-19, and figures from the U.K. Transport Department indicate that all of the airports serving London will be full by 2030—and perhaps by 2025, if no new runways are built.

The Airports Commission, launched last November, is due this year to report assessments and recommendations to improve airport capacity in the next five years, but it will not announce longer-term recommendations, for the next 25-30 years, until the summer of 2015, after the next election.

Tap the icon in the digital edition of AW&ST to see proposed alternatives for a third runway at Heathrow, or go to AviationWeek.com/heathrow