London Heathrow handled £293 billion worth of goods last year — more than 25% of all UK trade by value — and the union representing its workers says the airport is full, with two runways, no spare capacity and nowhere left to grow.

That capacity ceiling is the backdrop to an escalation in the push to build Heathrow's third runway. The GMB Union, one of the UK's largest trade unions, is calling for "spades in the ground" and has warned opponents against exploiting delays in the revised project timeline to argue for cancelling it altogether.

The union blames the UK's slow planning system for the hold-up and insists the answer is to fix that system, not abandon what it calls "one of the country's most important infrastructure projects."

"Opponents of this runway will try to dress up a timetable as a verdict. It isn't one. A project taking longer to build is not a reason not to build it. It's a reason to start now," said Warren Kenny, London Regional Secretary of the GMB Union. "Heathrow has been clear that the hold-up is planning and red tape. Politicians can fix that. The Chancellor is right to be clearing bottlenecks, and we want to see that go further and faster. Finalise the framework, hold the vote and get building."

Kenny put a hard number on the stakes: 108,000 jobs. "Every year of dithering is a year of apprenticeships not started, contracts not signed and wages not paid. Our members aren't waiting for 2039. The jobs start the day the spades go in the ground," he said.

Revised timeline, same target

Heathrow has revised its schedule for the project but maintains its core targets. The airport's current estimate is that it will secure planning permission by 2029 and open the new runway within a decade of that milestone.

"It's right that ambitious targets were set, the sooner expansion begins the sooner the whole UK will benefit. Our focus has always been to secure planning permission by 2029. Once achieved the runway will be open within a decade – and the benefits of expansion can be felt from today," a Heathrow spokesperson said.

The spokesperson pointed to "at least 108,000 new jobs and £ billions invested in supply chains in every part of the country," and stressed that the project is 100% privately financed. "This is a national project which will support growth today and secure the UK's position in the global economy once the runway opens," the spokesperson added.

Heathrow also confirmed its commitment to working with surrounding communities to ensure expansion plans are responsible, noting that recent polling from local voices indicates support for expansion exists among those living near the hub.

Competitiveness argument

The GMB's case extends beyond construction jobs. The union frames the third runway as a question of international competitiveness, arguing that Heathrow's capacity constraints are already diverting trade to rival European hubs.

"Every year without a third runway is a year that new trade goes to France, Germany and the Netherlands instead of Britain," the union said.

The framing carries weight given Heathrow's role as "Britain's biggest port by value." With more than a quarter of UK trade by value passing through the airport's cargo operations, constraints on runway capacity translate directly into constraints on the country's ability to grow air freight volumes — a concern for shippers, forwarders and carriers that rely on the hub for bellyhold capacity.

The union's intervention also broadens the political coalition behind the project. Heathrow's expansion is backed by trade unions, business groups, airports and communities across the UK, according to the airport — an alignment that could prove decisive if the government moves to finalise the planning framework and hold the parliamentary vote the GMB is demanding.

The immediate question for the freight sector is whether political momentum translates into procedural speed. With Heathrow targeting planning consent by 2029 and the union pressing for a vote now, the pace of the UK planning system — not financing, at 100% private capital — will determine when additional capacity at Britain's most valuable trade gateway becomes a reality.