Two proposals for expansion at London Heathrow each foresee a third runway – albeit of different lengths – becoming operational in 2035, with supporting developments including new terminal buildings.

Heathrow’s operator has submitted a proposal centred on a privately-financed third runway while the UK government has also permitted a rival organisation, Arora Group, to submit its own competing proposition.

The Heathrow operator’s £49 billion ($65 billion) plan focuses on developing the northwest area of the hub with a £21 billion runway up to 3,500m in length.

This would be complemented by a new terminal – designated T5X, sited adjacent and parallel to the third runway – plus an expanded Terminal 2 and new satellite terminals. Terminal 3 would be closed.

T5X would cost £12 billion. The operator adds that a £15 billion redevelopment of the current central terminal area is already planned, irrespective of the third runway, but has been included in the submission for practical purposes.

The competing Arora Group plan also features a northwest runway, about 2,800m long, but otherwise concentrates on the western side of the airport.

It proposes expanding Terminal 5 westward to create an adjoining Terminal 6, comprising two phases: T6A, which would open in 2036, and T6B in 2040.

Arora Group has not disclosed an investment figure for the development, devised in co-operation with airport engineering and construction specialist Bechtel, but says the proposal is “costed”.

It points out that its ‘Heathrow West’ proposition will reduce risk by avoiding crossing the orbital M25 highway which circles London and passes 1km from the airport’s western side.

Arora Group says the combination of a shorter runway, fewer dependencies, and efficient construction programme “strongly suggests” that it can deliver the third runway in the government’s target timeframe, “if not sooner”.

It also claims that its proposal offers a “more acceptable and cost-effective solution”.

The Heathrow operator’s proposal acknowledges that its longer runway would require “realignment” of the M25 in order to build over it.

But the operator says its plan will increase the hub’s passenger capacity to 150 million and offer at least 30 new daily routes.

It says the government needs to put an “appropriate regulatory framework” in place to secure the necessary private capital from equity shareholders and debt investors.

But it adds that, if the government “moves at pace” with necessary policy changes, its “shovel-ready” proposal could receive planning permission by 2029, with a third runway operational “within a decade”.