Airport officials say the original 2035 deadline is no longer achievable, reigniting criticism over the long-contested expansion project.
The Greater Manchester mayor said he would wait for the outcome of a public consultation before taking a position on the £33bn expansion scheme.
The UK's busiest airport says it may miss the government's 2035 target, as ministers acknowledge the deadline has 'always been ambitious', the BBC reports.
With ticket prices high and ridership low, expansion plans could push London to rethink how passengers travel to and from the airport.
Anadolu Agency reports Istanbul Airport has taken the top spot in a global connectivity ranking, linking to 337 destinations, while London Heathrow's standing declined amid regional instability in the Middle East.
The UK government's climate advisers say the proposed expansion cannot be approved under current climate policies unless airlines help pay for greener aviation technology.
The UK's Climate Change Committee warns that a third runway would breach carbon budgets unless aviation emissions are offset through funded CO2 removal.
Nearly 180 flights were cancelled on Wednesday, following a technical outage that caused 1,300 flights to be cancelled across several British airports.
Departures from several UK airports have been affected by a technical issue involving air traffic control provider Nats, according to the BBC.
London airports hit hardest as disruption ripples across Europe; airlines call for overhaul of UK air traffic system